Weight Loss Calculator with Steps – Plan Your Journey
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Calculate Your Weight Loss Journey
Your Weight Loss Summary
—
Assumptions Made
- 1 lb of fat ≈ 3500 calories.
- BMR Calculated using .
- Activity Factor: .
Projected Weight Loss Over Time
Weight Loss Progression
| Week |
Starting Weight (lbs) |
Ending Weight (lbs) |
Weight Lost (lbs) |
Target Calorie Intake |
| Enter details and press Calculate. |
What is a Weight Loss Calculator with Steps?
A **weight loss calculator with steps** is a dynamic online tool designed to help individuals plan and track their weight management journey. It takes into account various personal metrics and lifestyle factors to provide personalized estimates for calorie intake, weekly weight loss targets, and the overall timeline required to reach a desired weight. Unlike simple calculators, this tool often breaks down the process into actionable steps, guiding users through the phases of their weight loss plan. It's not just about numbers; it's about providing a clear, data-driven roadmap for a healthier lifestyle.
This type of calculator is invaluable for anyone looking to lose weight in a structured and sustainable manner. Whether you're aiming to shed a few pounds or make a significant body transformation, understanding the science behind weight loss can demystify the process. Common misconceptions often revolve around crash diets or expecting rapid, unrealistic results. A well-designed weight loss calculator with steps aims to counter these myths by emphasizing gradual, consistent progress, which is crucial for long-term success and overall health. It empowers users with knowledge, helping them set realistic expectations and make informed decisions about their diet and exercise regimes.
Who Should Use It?
Anyone embarking on a weight loss journey can benefit from a **weight loss calculator with steps**. This includes:
- Individuals seeking to lose weight for health reasons (e.g., reducing risk of diabetes, heart disease).
- People who want to improve their physical fitness and energy levels.
- Those preparing for specific events where weight management is a goal.
- Individuals who have tried dieting before without success and need a more structured approach.
- Anyone looking for a personalized estimate of how long it might take to reach their goal weight, based on safe and effective weight loss principles.
Common Misconceptions Addressed
This calculator helps debunk myths such as:
- "Rapid weight loss is always best." Our calculator promotes a safe, sustainable rate (1-2 lbs per week), which is more likely to be maintained.
- "Calorie counting is the only factor." While critical, the calculator also factors in activity levels and metabolism for a holistic view.
- "Everyone loses weight at the same pace." Individual BMR, activity, and adherence significantly impact results, which the calculator helps estimate.
Weight Loss Calculator with Steps Formula and Mathematical Explanation
The core of any effective **weight loss calculator with steps** lies in understanding energy balance: the relationship between calories consumed and calories expended. To lose weight, one must create a calorie deficit – expending more calories than are consumed. The fundamental principle is that approximately 3,500 calories equate to one pound of body fat.
Step-by-Step Derivation
- Calculate Total Weight to Lose: This is the straightforward difference between current weight and target weight.
Total Weight to Lose (lbs) = Current Weight (lbs) - Target Weight (lbs)
- Calculate Target Daily Calorie Deficit: Based on the user's desired weekly weight loss, we determine the necessary daily deficit.
Target Weekly Calorie Deficit = Target Weekly Weight Loss (lbs) * 3500 calories/lb
Target Daily Calorie Deficit = Target Weekly Calorie Deficit / 7 days
- Calculate Basal Metabolic Rate (BMR): This is the number of calories the body burns at rest to maintain basic functions. We use either the Mifflin-St Jeor or Revised Harris-Benedict equations:
Mifflin-St Jeor Equation (often considered more accurate):
- For Men:
BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) + 5
- For Women:
BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) - 161
Revised Harris-Benedict Equation:
- For Men:
BMR = (13.397 * weight in kg) + (4.799 * height in cm) - (5.677 * age in years) + 88.362
- For Women:
BMR = (9.247 * weight in kg) + (3.098 * height in cm) - (4.330 * age in years) + 447.593
Note: Weight and height inputs need conversion if not provided in metric units. For this calculator, we use lbs and inches, requiring conversion: 1 lb = 0.453592 kg, 1 inch = 2.54 cm.
- Calculate Total Daily Energy Expenditure (TDEE): This estimates the total calories burned per day, including activity. TDEE is calculated by multiplying BMR by an activity factor:
TDEE = BMR * Activity Factor
Activity Factors:
- Sedentary: 1.2
- Lightly Active: 1.375
- Moderately Active: 1.55
- Very Active: 1.725
- Extra Active: 1.9
- Calculate Estimated Daily Calorie Intake: To achieve the target daily deficit, subtract it from the TDEE.
Estimated Daily Calorie Intake = TDEE - Target Daily Calorie Deficit
- Calculate Estimated Weeks to Reach Goal: Divide the total weight to lose by the target weekly loss.
Estimated Weeks to Reach Goal = Total Weight to Lose / Target Weekly Weight Loss
Variables Explained
| Variable |
Meaning |
Unit |
Typical Range |
| Current Weight |
The user's starting weight. |
Pounds (lbs) |
Varies widely; e.g., 100 – 500+ |
| Target Weight |
The user's desired final weight. |
Pounds (lbs) |
Varies widely; e.g., 100 – 300+ |
| Target Weekly Weight Loss |
The desired rate of weight reduction per week. |
Pounds (lbs) / week |
0.5 – 2.0 (Recommended: 1-2) |
| Age |
The user's age. |
Years |
1 – 120 |
| Gender |
Biological sex, impacts BMR formulas. |
Male / Female |
N/A |
| Height |
The user's physical height. |
Inches (in) |
Varies widely; e.g., 48 – 84 |
| Daily Activity Level |
Multiplier reflecting daily physical exertion. |
Categorical (Sedentary, Light, etc.) |
N/A |
| BMR Calculation Method |
Algorithm used to estimate resting metabolism. |
Categorical (Mifflin-St Jeor, Harris-Benedict) |
N/A |
| BMR |
Calories burned at complete rest. |
Calories / day |
~1000 – 2500+ |
| TDEE |
Total calories burned daily including activity. |
Calories / day |
~1500 – 3500+ |
| Daily Calorie Deficit |
Required calorie surplus for target weight loss. |
Calories / day |
~500 – 1000 (for 1-2 lbs/week) |
| Estimated Daily Calorie Intake |
Target calorie consumption for weight loss. |
Calories / day |
~1200 – 2500 (variable) |
| Estimated Weeks |
Timeframe to reach target weight. |
Weeks |
Varies |
Practical Examples (Real-World Use Cases)
Example 1: Sustainable Weight Loss for an Office Worker
Scenario: Sarah is a 35-year-old female, weighs 170 lbs, and wants to reach 150 lbs. She works an office job (sedentary) but walks moderately during lunch breaks. She aims for a sustainable weight loss of 1 lb per week. She uses the Mifflin-St Jeor method.
- Inputs:
- Current Weight: 170 lbs
- Target Weight: 150 lbs
- Target Weekly Weight Loss: 1 lb
- Age: 35
- Gender: Female
- Height: 65 inches
- Daily Activity Level: Lightly Active (approximating her walks)
- BMR Method: Mifflin-St Jeor
- Calculations (Simplified):
- Total Weight to Lose: 170 – 150 = 20 lbs
- Target Weekly Calorie Deficit: 1 lb * 3500 = 3500 calories
- Target Daily Calorie Deficit: 3500 / 7 = 500 calories
- BMR (Mifflin-St Jeor, approx.): ~1450 calories
- TDEE (with Light Activity Factor 1.375): ~1450 * 1.375 ≈ 1994 calories
- Estimated Daily Calorie Intake: 1994 – 500 = 1494 calories
- Estimated Weeks to Reach Goal: 20 lbs / 1 lb/week = 20 weeks
- Interpretation: Sarah needs to consistently consume around 1500 calories per day and aim for a 500-calorie deficit to lose 1 lb per week. It will likely take her about 20 weeks to reach her goal. This provides a clear target for her daily meals and helps manage expectations. She can use this information to plan healthier meals within her calorie budget.
Example 2: Faster Weight Loss for an Active Individual
Scenario: David is a 40-year-old male, weighs 220 lbs, and wants to reach 190 lbs. He exercises vigorously 5 days a week. He aims for a 2 lb weekly weight loss. He uses the Revised Harris-Benedict method.
- Inputs:
- Current Weight: 220 lbs
- Target Weight: 190 lbs
- Target Weekly Weight Loss: 2 lbs
- Age: 40
- Gender: Male
- Height: 72 inches
- Daily Activity Level: Very Active
- BMR Method: Harris-Benedict (Revised)
- Calculations (Simplified):
- Total Weight to Lose: 220 – 190 = 30 lbs
- Target Weekly Calorie Deficit: 2 lbs * 3500 = 7000 calories
- Target Daily Calorie Deficit: 7000 / 7 = 1000 calories
- BMR (Revised Harris-Benedict, approx.): ~1850 calories
- TDEE (with Very Active Factor 1.725): ~1850 * 1.725 ≈ 3191 calories
- Estimated Daily Calorie Intake: 3191 – 1000 = 2191 calories
- Estimated Weeks to Reach Goal: 30 lbs / 2 lbs/week = 15 weeks
- Interpretation: David needs a substantial daily deficit of 1000 calories. His estimated daily intake is around 2200 calories. To achieve 2 lbs loss per week, maintaining this deficit requires significant commitment to both diet and exercise. This goal might be ambitious and requires careful monitoring. The calculator highlights that a 2 lb/week loss is aggressive and may require further adjustment based on his body's response.
How to Use This Weight Loss Calculator with Steps
Using our **weight loss calculator with steps** is designed to be intuitive and provide actionable insights. Follow these simple steps to get started:
- Enter Your Current Weight: Input your weight in pounds (lbs) as accurately as possible. This is your starting point.
- Set Your Target Weight: Enter the weight in pounds (lbs) you aim to achieve. Be realistic and consider health recommendations.
- Define Your Weekly Loss Rate: Specify how many pounds you intend to lose each week. For sustainable and healthy weight loss, a rate of 1-2 lbs per week is generally recommended.
- Select Your Daily Activity Level: Choose the option that best describes your typical daily physical activity. This helps estimate your total daily energy expenditure (TDEE).
- Choose BMR Calculation Method: Select either the Mifflin-St Jeor or Revised Harris-Benedict equation. Mifflin-St Jeor is often preferred for its accuracy.
- Provide Personal Details: Enter your age, gender, and height (in inches). These are crucial for calculating your Basal Metabolic Rate (BMR).
- Press Calculate: Once all fields are filled, click the "Calculate" button.
How to Read the Results
- Main Result (Estimated Weeks to Reach Goal): This prominent number shows the estimated time in weeks it will take to achieve your target weight, based on your inputs.
- Total Weight to Lose: The total amount of weight you need to lose in pounds.
- Estimated Weeks to Reach Goal: The projected duration of your weight loss journey.
- Daily Calorie Deficit Needed: The approximate number of calories you need to burn more than you consume each day.
- Estimated Daily Calorie Intake: The recommended daily calorie consumption to achieve your target deficit and weight loss rate.
- Assumptions Made: Understand the basis of the calculations (e.g., 3500 calories per pound of fat).
- Weight Loss Progression Table & Chart: Visualize your journey week by week, seeing projected weight changes and calorie targets.
Decision-Making Guidance
The results from this **weight loss calculator with steps** can inform several key decisions:
- Setting Realistic Goals: The estimated weeks provide a timeframe, helping you adjust expectations and stay motivated. If the timeline seems too long, consider if your target weight is realistic or if a slightly higher weekly loss rate (within safe limits) is feasible.
- Calorie Management: The estimated daily calorie intake is your guide for meal planning. You can use this number to create balanced, nutritious meals that fit within your budget.
- Exercise Planning: The activity level input influences your TDEE. If you find the required calorie intake too low, increasing your activity level (and thus TDEE) can create a larger deficit, potentially shortening the timeline or allowing for a higher calorie intake.
- Monitoring Progress: Use the weekly progression table and chart to track your actual weight loss against the projections. If you're consistently losing more or less than projected, you may need to adjust your calorie intake or activity levels.
Remember, this calculator provides an estimate. Individual results can vary due to metabolic differences, adherence to the plan, hormonal factors, and other health conditions. It's always advisable to consult with a healthcare professional or registered dietitian before making significant changes to your diet or exercise routine.
Key Factors That Affect Weight Loss Calculator Results
While a **weight loss calculator with steps** provides valuable estimates, numerous factors can influence actual outcomes. Understanding these nuances is critical for a successful and realistic weight loss journey.
- Metabolic Adaptation: As you lose weight, your body's metabolism can slow down. Your BMR and TDEE decrease because you have less body mass to maintain. A calculator typically uses initial values, so you might need to recalculate or adjust your intake as you progress to maintain the same rate of loss. This is a crucial aspect of long-term weight management.
- Body Composition Changes: Weight loss isn't just about losing fat; it can also involve losing muscle mass, especially with aggressive calorie restriction or insufficient protein intake. Muscle tissue burns more calories than fat tissue, so preserving muscle is key to maintaining a healthy metabolism. The calculator doesn't directly measure body composition, which can affect calorie expenditure.
- Hormonal Fluctuations: Hormones like cortisol (stress), thyroid hormones, insulin, and leptin play significant roles in appetite regulation, fat storage, and metabolism. Stress, sleep deprivation, and underlying conditions can disrupt hormonal balance, impacting how effectively your body loses weight, regardless of calorie deficit.
- Adherence and Consistency: The most significant factor is how closely you stick to the calculated calorie intake and activity plan. A perfect plan is useless if not followed. Even small deviations can add up over time, affecting the projected timeline. For instance, consistently exceeding your target calorie intake by 100 calories per day could add weeks to your journey.
- Digestive Health and Nutrient Absorption: The efficiency of your digestive system can influence how many calories and nutrients you absorb from food. Issues like leaky gut or specific dietary choices can impact nutrient utilization and overall energy balance.
- Hydration Levels: Water is essential for numerous bodily functions, including metabolism and appetite regulation. Proper hydration can support weight loss efforts, while dehydration can hinder them. The calculator assumes optimal hydration supports metabolic processes.
- Medications and Health Conditions: Certain medications (e.g., corticosteroids, antidepressants) and medical conditions (e.g., PCOS, hypothyroidism) can affect metabolism, appetite, and weight regulation, potentially altering the results predicted by a standard calculator.
- Exercise Intensity and Type: While the calculator uses general activity levels, the specific type, intensity, and duration of exercise matter. High-intensity interval training (HIIT), for example, can have a greater impact on calorie burn and metabolic rate than steady-state cardio alone. The calculator's "activity factor" is a broad estimate.
For precise **weight loss calculator with steps** outputs, it's vital to view the results as a starting point and be prepared to adapt your strategy based on your body's unique response and lifestyle factors.
Frequently Asked Questions (FAQ)
- Q1: Is a 1-2 lb per week weight loss rate healthy and sustainable?
- A: Yes, for most individuals, a weight loss of 1-2 lbs per week is considered healthy and sustainable. It typically involves a deficit of 500-1000 calories per day, which is generally achievable through diet and exercise without extreme deprivation. Faster rates can lead to muscle loss and are harder to maintain long-term.
- Q2: What if my target weight seems unrealistic based on the calculator's timeline?
- A: If the timeline is very long, reassess your target weight. Is it a healthy weight for your height and frame? Consult BMI charts or a healthcare provider. Alternatively, consider if a slightly more ambitious (but still safe) weekly loss rate is appropriate for you, keeping in mind the increased difficulty and potential risks.
- Q3: Why does the calculator ask for age, gender, and height?
- A: These factors are essential for calculating your Basal Metabolic Rate (BMR) – the calories your body burns at rest. Men generally have higher BMRs than women due to differences in muscle mass. BMR also tends to decrease with age and varies with height and weight.
- Q4: How accurate is the calorie deficit estimation?
- A: Calorie deficit estimations are based on averages and formulas (like Mifflin-St Jeor or Harris-Benedict). Individual metabolic rates can vary significantly. The calculator provides a strong estimate, but you may need to fine-tune your intake based on your actual results.
- Q5: Does the calculator account for water weight fluctuations?
- A: No, the calculator primarily estimates fat loss based on a consistent calorie deficit. Water weight can fluctuate daily due to hydration, sodium intake, and hormonal changes, and is not directly factored into the long-term projection.
- Q6: Can I eat less than the calculated 'Estimated Daily Calorie Intake'?
- A: While possible, it's generally not recommended to go below 1200 calories per day for women or 1500 calories per day for men without medical supervision. Very low-calorie diets can be detrimental to health, slow metabolism, and lead to nutrient deficiencies.
- Q7: How often should I update my inputs in the calculator?
- A: It's beneficial to update your inputs (especially current weight) every 4-6 weeks, or whenever you hit a plateau. As you lose weight, your BMR and TDEE decrease, requiring adjustments to maintain your target deficit and weight loss rate.
- Q8: What does 'Activity Factor' mean in the context of weight loss?
- A: The Activity Factor is a multiplier used to estimate your Total Daily Energy Expenditure (TDEE). It accounts for the calories burned through daily activities and planned exercise beyond your BMR. Higher activity levels require a higher factor, meaning you burn more calories throughout the day.
- Q9: Does the calculator consider different types of fats (e.g., visceral vs. subcutaneous)?
- A: No, the calculator operates on the general principle that approximately 3500 calories equal one pound of body fat. It doesn't differentiate between types of fat stores. The primary goal is overall fat reduction.
Related Tools and Internal Resources
// — Input Validation —
function validateInput(id, errorId, min, max, allowDecimal = true) {
var input = document.getElementById(id);
var errorElement = document.getElementById(errorId);
var value = parseFloat(input.value);
errorElement.textContent = "; // Clear previous error
if (isNaN(value)) {
errorElement.textContent = 'Please enter a valid number.';
return false;
}
if (!allowDecimal && !Number.isInteger(value)) {
errorElement.textContent = 'Please enter a whole number.';
return false;
}
if (value max) {
errorElement.textContent = 'Value cannot be greater than ' + max + '.';
return false;
}
return true;
}
// — Helper Functions —
function lbsToKg(lbs) {
return lbs * 0.453592;
}
function inchesToCm(inches) {
return inches * 2.54;
}
function getActivityFactor(level) {
switch (level) {
case 'sedentary': return 1.2;
case 'light': return 1.375;
case 'moderate': return 1.55;
case 'very_active': return 1.725;
case 'extra_active': return 1.9;
default: return 1.2;
}
}
// — BMR Calculation —
function calculateBMR(weightKg, heightCm, age, gender, method) {
var bmr = 0;
if (method === 'mifflin_st_jeor') {
if (gender === 'male') {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161;
}
} else { // Revised Harris-Benedict
if (gender === 'male') {
bmr = (13.397 * weightKg) + (4.799 * heightCm) – (5.677 * age) + 88.362;
} else {
bmr = (9.247 * weightKg) + (3.098 * heightCm) – (4.330 * age) + 447.593;
}
}
return bmr;
}
// — Main Calculation Logic —
var weightLossChartInstance = null; // To hold the chart instance
function calculateWeightLoss() {
// Clear previous errors
document.getElementById('currentWeightError').textContent = ";
document.getElementById('targetWeightError').textContent = ";
document.getElementById('weeklyLossRateError').textContent = ";
document.getElementById('ageError').textContent = ";
document.getElementById('heightError').textContent = ";
// Validate inputs
var isValid = true;
isValid = validateInput('currentWeight', 'currentWeightError', 1, 1000) && isValid;
isValid = validateInput('targetWeight', 'targetWeightError', 1, 1000) && isValid;
isValid = validateInput('weeklyLossRate', 'weeklyLossRateError', 0.1, 5) && isValid; // Allow decimals, up to 5 lbs/week
isValid = validateInput('age', 'ageError', 1, 120) && isValid;
isValid = validateInput('height', 'heightError', 10, 96) && isValid; // Height in inches
var currentWeight = parseFloat(document.getElementById('currentWeight').value);
var targetWeight = parseFloat(document.getElementById('targetWeight').value);
var weeklyLossRate = parseFloat(document.getElementById('weeklyLossRate').value);
var age = parseInt(document.getElementById('age').value);
var heightInches = parseFloat(document.getElementById('height').value);
var gender = document.getElementById('gender').value;
var bmrMethod = document.getElementById('bmrMethod').value;
var activityLevel = document.getElementById('dailyActivityLevel').value;
if (currentWeight <= targetWeight) {
document.getElementById('targetWeightError').textContent = 'Target weight must be less than current weight.';
isValid = false;
}
if (!isValid) {
resetResults(); // Clear results if validation fails
return;
}
// Conversions
var weightKg = lbsToKg(currentWeight);
var heightCm = inchesToCm(heightInches);
// Calculations
var totalWeightToLose = currentWeight – targetWeight;
var targetWeeklyCalorieDeficit = weeklyLossRate * 3500;
var targetDailyCalorieDeficit = targetWeeklyCalorieDeficit / 7;
var bmr = calculateBMR(weightKg, heightCm, age, gender, bmrMethod);
var activityFactor = getActivityFactor(activityLevel);
var tdee = bmr * activityFactor;
var estimatedDailyIntake = tdee – targetDailyCalorieDeficit;
// Ensure estimated intake is not unrealistically low
if (estimatedDailyIntake < 1200 && gender === 'female') {
estimatedDailyIntake = 1200;
document.getElementById('dailyCalorieDeficit').textContent = (tdee – estimatedDailyIntake).toFixed(0) + ' calories';
} else if (estimatedDailyIntake < 1500 && gender === 'male') {
estimatedDailyIntake = 1500;
document.getElementById('dailyCalorieDeficit').textContent = (tdee – estimatedDailyIntake).toFixed(0) + ' calories';
} else {
document.getElementById('dailyCalorieDeficit').textContent = targetDailyCalorieDeficit.toFixed(0) + ' calories';
}
var estimatedWeeks = totalWeightToLose / weeklyLossRate;
// Display Results
document.getElementById('mainResult').textContent = estimatedWeeks.toFixed(1) + ' Weeks';
document.getElementById('totalWeightToLose').textContent = totalWeightToLose.toFixed(1) + ' lbs';
document.getElementById('estimatedWeeks').textContent = estimatedWeeks.toFixed(1) + ' weeks';
document.getElementById('estimatedDailyIntake').textContent = estimatedDailyIntake.toFixed(0) + ' calories';
document.getElementById('bmrMethodUsed').textContent = bmrMethod.replace('_', ' ').toUpperCase();
document.getElementById('activityFactorUsed').textContent = activityFactor + ' (' + activityLevel.replace('_', ' ') + ')';
// Update Table and Chart
updateProgressionTable(currentWeight, weeklyLossRate, estimatedWeeks, estimatedDailyIntake, totalWeightToLose);
updateChart(estimatedWeeks, currentWeight, weeklyLossRate, estimatedDailyIntake);
}
function resetResults() {
document.getElementById('mainResult').textContent = '–';
document.getElementById('totalWeightToLose').textContent = '–';
document.getElementById('estimatedWeeks').textContent = '–';
document.getElementById('estimatedDailyIntake').textContent = '–';
document.getElementById('dailyCalorieDeficit').textContent = '–';
document.getElementById('bmrMethodUsed').textContent = '–';
document.getElementById('activityFactorUsed').textContent = '–';
var tableBody = document.getElementById('progressionTableBody');
tableBody.innerHTML = '
| Enter details and press Calculate. |
';
if (weightLossChartInstance) {
weightLossChartInstance.destroy();
weightLossChartInstance = null;
}
var canvas = document.getElementById('weightLossChart');
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear canvas content
}
function resetCalculator() {
document.getElementById('currentWeight').value = '180';
document.getElementById('targetWeight').value = '150';
document.getElementById('weeklyLossRate').value = '1.5';
document.getElementById('dailyActivityLevel').value = 'moderate';
document.getElementById('bmrMethod').value = 'mifflin_st_jeor';
document.getElementById('gender').value = 'female';
document.getElementById('age').value = '30';
document.getElementById('height').value = '66'; // Example height in inches
// Clear errors
document.getElementById('currentWeightError').textContent = ";
document.getElementById('targetWeightError').textContent = ";
document.getElementById('weeklyLossRateError').textContent = ";
document.getElementById('ageError').textContent = ";
document.getElementById('heightError').textContent = ";
resetResults();
}
// — Charting Logic (using Canvas API) —
function updateChart(estimatedWeeks, startWeight, weeklyLossRate, dailyIntake) {
var canvas = document.getElementById('weightLossChart');
var ctx = canvas.getContext('2d');
// Clear previous chart
if (weightLossChartInstance) {
weightLossChartInstance.destroy();
}
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear canvas content
var maxWeeks = Math.ceil(estimatedWeeks);
var weeksData = [];
var weightData = [];
var calorieData = []; // For projected intake if needed, or just a flat line for reference
// Simulate data points up to estimated weeks or a reasonable limit (e.g., 52 weeks)
var limitWeeks = Math.min(Math.ceil(estimatedWeeks) + 1, 52); // Show up to 52 weeks max
for (var i = 0; i <= limitWeeks; i++) {
weeksData.push(i);
var projectedWeight = startWeight – (i * weeklyLossRate);
weightData.push(Math.max(projectedWeight, parseFloat(document.getElementById('targetWeight').value))); // Don't go below target
calorieData.push(parseInt(dailyIntake)); // Reference line for target intake
}
// Basic Chart Styling
var chartWidth = canvas.width;
var chartHeight = canvas.height;
var padding = 40;
var chartAreaWidth = chartWidth – 2 * padding;
var chartAreaHeight = chartHeight – 2 * padding;
// Find max and min values for scaling
var maxWeight = startWeight;
var minWeight = Math.min.apply(null, weightData);
var weightRange = maxWeight – minWeight;
// Draw Axes
ctx.strokeStyle = '#ccc';
ctx.lineWidth = 1;
// Y-axis (Weight)
ctx.beginPath();
ctx.moveTo(padding, padding);
ctx.lineTo(padding, chartHeight – padding);
ctx.stroke();
ctx.fillText('Weight (lbs)', padding – 35, padding / 2); // Y-axis label
// X-axis (Weeks)
ctx.beginPath();
ctx.moveTo(padding, chartHeight – padding);
ctx.lineTo(chartWidth – padding, chartHeight – padding);
ctx.stroke();
ctx.fillText('Weeks', chartWidth / 2 – 20, chartHeight – padding / 2); // X-axis label
// Draw Data Series: Projected Weight Loss
ctx.beginPath();
ctx.moveTo(padding, chartHeight – padding); // Start at week 0
for (var i = 0; i < weeksData.length; i++) {
var x = padding + (weeksData[i] / limitWeeks) * chartAreaWidth;
var y = chartHeight – padding – ((weightData[i] – minWeight) / weightRange) * chartAreaHeight;
if (i === 0) {
ctx.moveTo(x, y);
} else {
ctx.lineTo(x, y);
}
}
ctx.strokeStyle = 'var(–primary-color)';
ctx.lineWidth = 2;
ctx.stroke();
ctx.fillStyle = 'rgba(0, 74, 153, 0.1)'; // Light fill
ctx.lineTo(chartWidth – padding, chartHeight – padding); // Close path for fill
ctx.fill();
// Draw Data Series: Target Calorie Intake (as a reference line)
ctx.beginPath();
var calorieY = chartHeight – padding – ((calorieData[0] – minWeight) / weightRange) * chartAreaHeight;
ctx.moveTo(padding, calorieY);
ctx.lineTo(chartWidth – padding, calorieY);
ctx.strokeStyle = 'var(–success-color)';
ctx.setLineDash([5, 5]); // Dashed line
ctx.lineWidth = 1.5;
ctx.stroke();
ctx.setLineDash([]); // Reset line dash
// Draw Axis Labels and Ticks
ctx.fillStyle = '#333';
ctx.textAlign = 'center';
ctx.textBaseline = 'top';
// X-axis ticks and labels
for (var i = 0; i < weeksData.length; i++) {
var x = padding + (weeksData[i] / limitWeeks) * chartAreaWidth;
ctx.moveTo(x, chartHeight – padding);
ctx.lineTo(x, chartHeight – padding + 5); // Tick mark
ctx.stroke();
if (weeksData[i] % 4 === 0 || weeksData[i] === limitWeeks) { // Label every 4 weeks or at the end
ctx.fillText(weeksData[i], x, chartHeight – padding + 10);
}
}
// Y-axis ticks and labels
ctx.textAlign = 'right';
ctx.textBaseline = 'middle';
var numTicks = 5;
for (var i = 0; i <= numTicks; i++) {
var y = chartHeight – padding – (i / numTicks) * chartAreaHeight;
var weightLabel = maxWeight – (i / numTicks) * weightRange;
ctx.moveTo(padding, y);
ctx.lineTo(padding – 5, y); // Tick mark
ctx.stroke();
ctx.fillText(weightLabel.toFixed(0), padding – 10, y);
}
// Legend
ctx.textAlign = 'left';
ctx.textBaseline = 'bottom';
ctx.fillStyle = '#333';
// Projected Weight
ctx.fillStyle = 'var(–primary-color)';
ctx.fillRect(padding + 5, padding + 5, 15, 5);
ctx.fillText('Projected Weight', padding + 25, padding + 5);
// Target Calorie Intake
ctx.fillStyle = 'var(–success-color)';
ctx.fillRect(padding + 5, padding + 20, 15, 5);
ctx.fillText('Target Calorie Intake', padding + 25, padding + 20);
}
// — Table Generation —
function updateProgressionTable(startWeight, weeklyLossRate, estimatedWeeks, dailyIntake, totalWeightToLose) {
var tableBody = document.getElementById('progressionTableBody');
tableBody.innerHTML = ''; // Clear existing rows
var numRows = Math.min(Math.ceil(estimatedWeeks) + 1, 53); // Show up to 52 weeks + start week
var currentWeight = startWeight;
for (var i = 0; i 0) {
weightLostThisWeek = Math.min(weeklyLossRate, currentWeight – parseFloat(document.getElementById('targetWeight').value)); // Don't lose more than needed
endingWeight = currentWeight – weightLostThisWeek;
if (endingWeight < parseFloat(document.getElementById('targetWeight').value)) {
endingWeight = parseFloat(document.getElementById('targetWeight').value);
weightLostThisWeek = currentWeight – endingWeight;
}
}
var cell0 = row.insertCell(0);
var cell1 = row.insertCell(1);
var cell2 = row.insertCell(2);
var cell3 = row.insertCell(3);
var cell4 = row.insertCell(4);
cell0.textContent = week === 0 ? 'Start' : week;
cell1.textContent = (week === 0 ? startWeight : currentWeight).toFixed(1);
cell2.textContent = endingWeight.toFixed(1);
cell3.textContent = weightLostThisWeek.toFixed(1);
cell4.textContent = (i === 0) ? '-' : Math.round(dailyIntake); // Target intake shown from week 1
currentWeight = endingWeight; // Update for the next iteration
if (currentWeight 0) {
// If target weight is reached, stop adding rows or show target consistently
if (i 1 && currentWeight > parseFloat(document.getElementById('targetWeight').value)) {
var lastRow = tableBody.rows[tableBody.rows.length – 1];
if (lastRow.cells[0].textContent !== 'Goal Reached') {
var row = tableBody.insertRow(tableBody.rows.length); // Insert at the end
var cell0 = row.insertCell(0);
var cell1 = row.insertCell(1);
var cell2 = row.insertCell(2);
var cell3 = row.insertCell(3);
var cell4 = row.insertCell(4);
cell0.textContent = 'Goal Reached';
cell1.textContent = currentWeight.toFixed(1);
cell2.textContent = parseFloat(document.getElementById('targetWeight').value).toFixed(1);
cell3.textContent = (currentWeight – parseFloat(document.getElementById('targetWeight').value)).toFixed(1);
cell4.textContent = Math.round(dailyIntake);
}
}
}
// — Copy Results —
function copyResults() {
var mainResult = document.getElementById('mainResult').textContent;
var totalWeightToLose = document.getElementById('totalWeightToLose').textContent;
var estimatedWeeks = document.getElementById('estimatedWeeks').textContent;
var estimatedDailyIntake = document.getElementById('estimatedDailyIntake').textContent;
var dailyCalorieDeficit = document.getElementById('dailyCalorieDeficit').textContent;
var bmrMethodUsed = document.getElementById('bmrMethodUsed').textContent;
var activityFactorUsed = document.getElementById('activityFactorUsed').textContent;
var assumptions = "Assumptions:\n";
assumptions += "- 1 lb of fat ≈ 3500 calories.\n";
assumptions += "- BMR Calculated using " + bmrMethodUsed + ".\n";
assumptions += "- Activity Factor: " + activityFactorUsed + ".\n";
var resultsText = "— Weight Loss Summary —\n";
resultsText += "Estimated Time to Reach Goal: " + mainResult + "\n";
resultsText += "Total Weight to Lose: " + totalWeightToLose + "\n";
resultsText += "Estimated Weeks: " + estimatedWeeks + "\n";
resultsText += "Daily Calorie Deficit Needed: " + dailyCalorieDeficit + "\n";
resultsText += "Estimated Daily Calorie Intake: " + estimatedDailyIntake + "\n\n";
resultsText += assumptions;
// Use a temporary textarea to copy text
var textArea = document.createElement("textarea");
textArea.value = resultsText;
textArea.style.position = "fixed";
textArea.style.left = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied to clipboard!' : 'Failed to copy results.';
// Optionally display a temporary message to the user
var tempMsgElement = document.createElement('div');
tempMsgElement.textContent = msg;
tempMsgElement.style.cssText = 'position: fixed; top: 50%; left: 50%; transform: translate(-50%, -50%); background-color: var(–success-color); color: white; padding: 15px; border-radius: 5px; z-index: 1000; font-size: 1.2em;';
document.body.appendChild(tempMsgElement);
setTimeout(function() {
document.body.removeChild(tempMsgElement);
}, 2000);
} catch (err) {
console.error('Copying text command was unsuccessful', err);
// Display error message
var tempMsgElement = document.createElement('div');
tempMsgElement.textContent = 'Copy failed. Please copy manually.';
tempMsgElement.style.cssText = 'position: fixed; top: 50%; left: 50%; transform: translate(-50%, -50%); background-color: #dc3545; color: white; padding: 15px; border-radius: 5px; z-index: 1000; font-size: 1.2em;';
document.body.appendChild(tempMsgElement);
setTimeout(function() {
document.body.removeChild(tempMsgElement);
}, 2000);
}
document.body.removeChild(textArea);
}
// Initialize calculator on load
document.addEventListener('DOMContentLoaded', function() {
// Initialize chart canvas dimensions
var canvas = document.getElementById('weightLossChart');
canvas.width = canvas.parentElement.offsetWidth * 0.95; // Make canvas responsive to parent width
canvas.height = 300; // Fixed height or make responsive too
resetCalculator(); // Load default values
});