Current Weight to Goal Weight Calculator

Current Weight to Goal Weight Calculator & Analysis body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f8f9fa; color: #333; line-height: 1.6; margin: 0; padding: 0; } .container { max-width: 1000px; margin: 20px auto; padding: 20px; background-color: #fff; border-radius: 8px; box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1); display: flex; flex-direction: column; align-items: center; } header { text-align: center; margin-bottom: 30px; border-bottom: 1px solid #eee; padding-bottom: 20px; width: 100%; } header h1 { color: #004a99; margin-bottom: 10px; font-size: 2.5em; } .calculator-section { width: 100%; max-width: 700px; margin-bottom: 40px; padding: 30px; background-color: #ffffff; border-radius: 8px; box-shadow: 0 0 15px rgba(0, 0, 0, 0.05); } .calculator-section h2 { color: #004a99; text-align: center; margin-bottom: 25px; font-size: 1.8em; } .input-group { margin-bottom: 20px; width: 100%; text-align: left; } .input-group label { display: block; margin-bottom: 8px; font-weight: bold; color: #555; } .input-group input[type="number"], .input-group select { width: calc(100% – 20px); padding: 12px; border: 1px solid #ccc; border-radius: 5px; font-size: 1em; box-sizing: border-box; transition: border-color 0.3s ease; } .input-group input[type="number"]:focus, .input-group select:focus { border-color: #004a99; outline: none; } .input-group .helper-text { font-size: 0.85em; color: #6c757d; margin-top: 5px; display: block; } .error-message { color: #dc3545; font-size: 0.9em; margin-top: 5px; display: none; /* Hidden by default */ min-height: 1.2em; /* Prevent layout shift */ } .btn-container { text-align: center; margin-top: 25px; } button { background-color: #004a99; color: white; border: none; padding: 12px 25px; border-radius: 5px; cursor: pointer; font-size: 1.1em; margin: 0 10px; transition: background-color 0.3s ease, transform 0.2s ease; } button:hover { background-color: #003366; transform: translateY(-2px); } button.reset-btn { background-color: #6c757d; } button.reset-btn:hover { background-color: #5a6268; } button.copy-btn { background-color: #28a745; } button.copy-btn:hover { background-color: #218838; } .results-container { margin-top: 30px; padding: 25px; background-color: #e9ecef; border-radius: 8px; text-align: center; width: 100%; box-sizing: border-box; } .results-container h3 { color: #004a99; margin-bottom: 20px; font-size: 1.5em; } #primary-result { font-size: 2.5em; font-weight: bold; color: #28a745; margin-bottom: 15px; display: inline-block; padding: 10px 20px; background-color: #d4edda; border-radius: 5px; } .intermediate-results { display: flex; justify-content: space-around; flex-wrap: wrap; gap: 15px; margin-bottom: 20px; } .intermediate-results div { background-color: #fff; padding: 15px 20px; border-radius: 5px; box-shadow: 0 1px 5px rgba(0,0,0,0.1); flex: 1; min-width: 150px; text-align: center; } .intermediate-results span { display: block; font-size: 1.3em; font-weight: bold; color: #004a99; } .intermediate-results p { font-size: 0.9em; color: #555; margin: 0; } .formula-explanation { font-size: 0.9em; color: #6c757d; margin-top: 15px; border-top: 1px dashed #ccc; padding-top: 15px; } .chart-container, .table-container { margin-top: 30px; padding: 25px; background-color: #ffffff; border-radius: 8px; box-shadow: 0 0 15px rgba(0, 0, 0, 0.05); width: 100%; box-sizing: border-box; } .chart-container h3, .table-container h3 { color: #004a99; text-align: center; margin-bottom: 20px; } canvas { max-width: 100%; height: auto; display: block; margin: 20px auto; } table { width: 100%; border-collapse: collapse; margin-top: 20px; } th, td { padding: 12px 15px; text-align: left; border-bottom: 1px solid #ddd; } th { background-color: #004a99; color: white; font-weight: bold; } tr:nth-child(even) { background-color: #f2f2f2; } caption { font-size: 0.9em; color: #6c757d; margin-top: 15px; caption-side: bottom; text-align: center; } .article-content { width: 100%; max-width: 960px; margin: 40px auto 0 auto; padding: 20px; background-color: #fff; border-radius: 8px; box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1); } .article-content h2, .article-content h3 { color: #004a99; margin-top: 30px; margin-bottom: 15px; } .article-content h1 { color: #004a99; text-align: center; margin-bottom: 20px; font-size: 2.2em; } .article-content p { margin-bottom: 15px; } .article-content ul, .article-content ol { margin-bottom: 15px; padding-left: 25px; } .article-content li { margin-bottom: 8px; } .faq-item { margin-bottom: 20px; border-left: 3px solid #004a99; padding-left: 15px; } .faq-item strong { display: block; color: #004a99; margin-bottom: 5px; } .internal-links-section ul { list-style: none; padding: 0; } .internal-links-section li { margin-bottom: 15px; background-color: #f8f9fa; padding: 10px; border-radius: 5px; border-left: 3px solid #28a745; } .internal-links-section a { color: #004a99; text-decoration: none; font-weight: bold; } .internal-links-section a:hover { text-decoration: underline; } .internal-links-section p { font-size: 0.9em; color: #555; margin-top: 5px; } .variable-table table { background-color: #fdfdfd; } .variable-table th, .variable-table td { padding: 10px 12px; } .results-summary { margin-top: 20px; font-size: 0.95em; color: #555; background-color: #eef7ff; padding: 15px; border-radius: 5px; } .highlight { color: #004a99; font-weight: bold; } .positive-change { color: #28a745; } .negative-change { color: #dc3545; } .neutral-change { color: #6c757d; } .copy-feedback { display: inline-block; margin-left: 10px; font-size: 0.9em; color: #28a745; opacity: 0; transition: opacity 0.5s ease; }

Current Weight to Goal Weight Calculator

Bridge the gap between where you are and where you want to be.

Calculate Your Weight Journey

Enter your current body weight.
Enter your desired body weight.
Kilograms (kg) Pounds (lbs) Select the unit of measurement for your weights.
Enter the desired weight change per week (e.g., 1 for 1 lb/kg loss, -1 for 1 lb/kg gain). Use positive for loss, negative for gain.

Your Weight Transformation Plan

Weight Difference

Estimated Weeks

Weekly Calorie Adjustment

Formula Used:

The core calculation determines the total weight difference needed. Estimated weeks are calculated by dividing the total difference by the desired weekly change rate. Weekly calorie adjustment is an approximation based on 3500 calories per pound (or 7700 per kg) of weight change.

Summary:

Projected Weight Change Over Time

Visualizing your projected weight journey based on your inputs.

Weight Change Milestones

Week Projected Weight Weight Change Since Start Change (lbs/kg)
Key milestones to track your progress towards your goal weight.

Understanding Your Current Weight to Goal Weight Journey

What is a Current Weight to Goal Weight Analysis?

A current weight to goal weight analysis is a fundamental tool for anyone looking to make significant changes to their body composition. It's not just about picking a number; it's about understanding the magnitude of change required, the estimated time it might take, and the physiological adjustments needed to achieve your target. This analysis helps individuals set realistic expectations and create a more informed approach to weight management, whether the goal is weight loss or weight gain.

Who Should Use It:

  • Individuals aiming to lose weight for health or aesthetic reasons.
  • Those seeking to gain muscle mass or healthy weight.
  • Athletes adjusting their weight class for competition.
  • Anyone looking for a structured, data-driven perspective on their body composition goals.

Common Misconceptions:

  • "It's just a simple subtraction." While subtraction is part of it, understanding the rate of change, metabolic adjustments, and individual biology adds crucial layers.
  • "Achieving a goal weight is always healthy." A goal weight should be within a healthy BMI range and suitable for the individual's frame and lifestyle. Rapid or extreme changes can be detrimental.
  • "The calculator guarantees results." This tool provides an estimate based on average physiological principles. Actual results depend on diet, exercise, genetics, and adherence.

Current Weight to Goal Weight Formula and Mathematical Explanation

The current weight to goal weight calculator uses a straightforward yet powerful set of formulas to estimate the journey ahead. The primary goal is to quantify the difference between your current and target weight and then project the time and effort needed to bridge that gap.

Step-by-Step Derivation:

  1. Calculate Total Weight Difference: This is the absolute difference between your current weight and your desired goal weight. It tells you how much weight you need to lose or gain in total.
  2. Calculate Estimated Time (Weeks): This step divides the total weight difference by your desired weekly rate of change. This gives you an estimated timeline.
  3. Calculate Weekly Calorie Adjustment: A common physiological principle states that approximately 3500 calories equate to one pound of body fat, and 7700 calories equate to one kilogram. This step uses this principle to estimate the weekly caloric surplus or deficit required to achieve the desired weekly weight change.

Variable Explanations:

Variable Meaning Unit Typical Range / Input Method
Current Weight Your current body mass. kg or lbs User Input
Goal Weight Your target body mass. kg or lbs User Input
Unit The system of measurement used. Select (kg/lbs)
Weekly Rate of Change Desired average change in weight per week. Positive for loss, negative for gain. kg/week or lbs/week User Input (e.g., 1 for 1 lb loss, -0.5 for 0.5 kg gain)
Total Weight Difference Absolute difference between current and goal weight. kg or lbs Calculated: |Current Weight – Goal Weight|
Estimated Weeks Projected time to reach goal based on weekly rate. Weeks Calculated: Total Weight Difference / |Weekly Rate of Change|
Weekly Calorie Adjustment Approximate weekly calorie deficit/surplus needed. Calories/week Calculated: Total Weight Difference * (3500 kcal/lb or 7700 kcal/kg) / Estimated Weeks

Practical Examples (Real-World Use Cases)

Example 1: Weight Loss Goal

Sarah wants to lose 20 pounds. Her current weight is 160 lbs, and her goal weight is 140 lbs. She aims for a sustainable weight loss of 1.5 pounds per week.

Inputs:

  • Current Weight: 160 lbs
  • Goal Weight: 140 lbs
  • Unit: lbs
  • Desired Weekly Change Rate: 1.5

Calculated Results:

  • Total Weight Difference: 20 lbs
  • Estimated Weeks: 13.33 weeks (approx. 3 months)
  • Weekly Calorie Adjustment: -5250 calories (a deficit of 5250 calories per week)

Interpretation: Sarah needs to create an average weekly calorie deficit of approximately 5250 calories to reach her goal weight in about 13-14 weeks. This could be achieved through a combination of diet and exercise.

Example 2: Weight Gain Goal (Muscle Building)

Mike wants to gain 10 pounds of muscle. His current weight is 170 lbs, and his goal weight is 180 lbs. He aims for a healthy gain of 0.5 pounds per week.

Inputs:

  • Current Weight: 170 lbs
  • Goal Weight: 180 lbs
  • Unit: lbs
  • Desired Weekly Change Rate: -0.5 (Negative because it's a gain)

Calculated Results:

  • Total Weight Difference: 10 lbs
  • Estimated Weeks: 20 weeks (approx. 5 months)
  • Weekly Calorie Adjustment: +1750 calories (a surplus of 1750 calories per week)

Interpretation: Mike needs to consume an average weekly surplus of 1750 calories to gain 10 pounds over 20 weeks. This surplus should ideally come from nutrient-dense foods to promote muscle growth rather than just fat gain.

How to Use This Current Weight to Goal Weight Calculator

Our calculator is designed for simplicity and clarity, providing actionable insights for your weight management goals. Follow these steps:

  1. Enter Current Weight: Input your exact current body weight in the designated field.
  2. Enter Goal Weight: Input your target body weight. Ensure this goal is realistic and healthy for your body frame and overall health objectives.
  3. Select Unit: Choose whether your weights are measured in kilograms (kg) or pounds (lbs). Consistency is key.
  4. Specify Weekly Change Rate: This is crucial. Enter a positive number (e.g., 1 or 2) if you want to lose weight (e.g., 1 lb or 1 kg per week). Enter a negative number (e.g., -0.5 or -1) if you want to gain weight (e.g., 0.5 lb or 1 lb per week). A rate of 1-2 lbs (or 0.5-1 kg) per week is generally considered safe and sustainable for weight loss. For weight gain, 0.5-1 lb per week is often recommended for lean mass accumulation.
  5. Click 'Calculate': The calculator will instantly process your inputs.

How to Read Results:

  • Primary Result (e.g., Estimated Weeks): This is your estimated timeline to reach your goal.
  • Weight Difference: The total amount of weight you need to gain or lose.
  • Weekly Calorie Adjustment: This provides an approximate weekly caloric target (deficit for loss, surplus for gain) to achieve your desired rate. Remember this is an estimate; individual metabolisms vary.
  • Chart and Table: These visualizations offer a clearer picture of your projected progress over time, helping you track milestones.

Decision-Making Guidance:

Use the results to inform your strategy. If the estimated time is longer than expected, consider if your weekly rate is too conservative or if your goal weight needs adjustment. The calorie adjustment figure is a powerful guide for planning your diet and exercise routines. Always consult with a healthcare professional or registered dietitian before making significant changes to your diet or exercise regimen.

Key Factors That Affect Current Weight to Goal Weight Results

While our calculator provides a solid estimate, numerous real-world factors can influence your actual progress. Understanding these can help you adjust your expectations and strategies:

  1. Metabolic Rate: Your basal metabolic rate (BMR) and total daily energy expenditure (TDEE) significantly impact how many calories you need. Factors like age, sex, muscle mass, and genetics play a role. A higher metabolic rate can speed up weight loss or require a larger calorie surplus for gain.
  2. Dietary Adherence and Quality: Simply aiming for a calorie deficit or surplus isn't enough. The quality of food matters. Nutrient-dense foods promote satiety and provide essential vitamins, while processed foods can lead to overconsumption and poor health outcomes, affecting both weight and overall well-being.
  3. Exercise Intensity and Type: The amount and type of physical activity influence calorie expenditure and body composition. Strength training, for instance, builds muscle, which can increase metabolism, while cardiovascular exercise burns calories directly. The calculator's calorie adjustment doesn't fully account for exercise variability.
  4. Hormonal Fluctuations: Hormones like cortisol, insulin, thyroid hormones, and sex hormones can profoundly affect appetite, fat storage, and metabolism. Conditions like PCOS or thyroid issues can make weight management more challenging.
  5. Sleep Quality and Stress Levels: Poor sleep and high stress levels can disrupt hormones that regulate appetite (ghrelin and leptin) and increase cortisol, often leading to increased cravings for unhealthy foods and fat storage, particularly around the midsection.
  6. Individual Physiology and Genetics: Everyone's body responds differently. Genetic predispositions can influence how easily you gain or lose weight, where you store fat, and your metabolic efficiency.
  7. Water Retention and Muscle Gain: Especially during the initial phases of weight loss or gain, changes in scale weight can be masked by fluctuations in water retention or concurrent muscle gain. This means the scale might not always reflect true fat loss or muscle gain accurately day-to-day or week-to-week.

Frequently Asked Questions (FAQ)

Q: Is a 1-2 lb per week weight loss rate safe and sustainable?

A: For most individuals, a weight loss rate of 1-2 pounds (0.5-1 kg) per week is considered safe and sustainable. This typically involves a deficit of 500-1000 calories per day. Faster rates can lead to muscle loss and other health issues.

Q: What if my goal weight results in a BMI outside the healthy range?

A: The calculator provides a numerical target. It's crucial to consider your overall health, body composition (muscle vs. fat mass), and a healthy Body Mass Index (BMI) range. If your goal weight seems inappropriate, consult a healthcare professional to set a more suitable and healthy target.

Q: How accurate is the calorie adjustment?

A: The calorie adjustment is an estimate based on a general rule (3500 kcal/lb or 7700 kcal/kg). Individual metabolic rates, non-exercise activity thermogenesis (NEAT), and the thermic effect of food (TEF) can cause variations. It serves as a starting point for dietary planning.

Q: Can I use different units (kg and lbs) in the same calculation?

A: No, for accurate results, ensure all weight inputs (current and goal) are in the same unit (either kg or lbs) as selected in the 'Unit' dropdown. The calculator works consistently within the chosen unit.

Q: What does a negative weekly rate of change mean?

A: A negative number for the 'Desired Weekly Change Rate' indicates a goal of *gaining* weight. For example, -0.5 lbs/week means you aim to gain 0.5 pounds each week.

Q: How often should I update my inputs in the calculator?

A: As your weight changes, or if your goals or lifestyle (e.g., exercise regimen) significantly change, it's beneficial to recalculate. This helps you stay on track and adjust your plan accordingly.

Q: Does this calculator consider muscle gain vs. fat loss?

A: The calculator focuses on total body weight change. While it provides calorie targets, it doesn't differentiate between muscle and fat. Achieving a healthy body composition requires a balanced approach focusing on nutrient intake and appropriate exercise, especially resistance training for muscle gain.

Q: How long will it take to see results on the scale?

A: While the calculator estimates weeks, initial weight changes can be influenced by factors like water loss/gain, and the body's adaptation. Consistent adherence to your plan is key, and it might take a few weeks to see consistent trends on the scale.

function getElement(id) { return document.getElementById(id); } function validateInput(inputId, errorId, minValue = null, maxValue = null) { var input = getElement(inputId); var errorDisplay = getElement(errorId); var value = parseFloat(input.value); var isValid = true; errorDisplay.style.display = 'none'; input.style.borderColor = '#ccc'; if (input.value.trim() === ") { errorDisplay.textContent = 'This field cannot be empty.'; errorDisplay.style.display = 'block'; input.style.borderColor = '#dc3545'; isValid = false; } else if (isNaN(value)) { errorDisplay.textContent = 'Please enter a valid number.'; errorDisplay.style.display = 'block'; input.style.borderColor = '#dc3545'; isValid = false; } else { if (minValue !== null && value maxValue) { errorDisplay.textContent = 'Value cannot be greater than ' + maxValue + '.'; errorDisplay.style.display = 'block'; input.style.borderColor = '#dc3545'; isValid = false; } } return isValid; } function calculateWeight() { var currentWeightInput = getElement('currentWeight'); var goalWeightInput = getElement('goalWeight'); var weightUnitSelect = getElement('weightUnit'); var weeklyRateInput = getElement('weeklyRate'); var resultsContainer = getElement('resultsContainer'); var primaryResultDisplay = getElement('primaryResult'); var weightDifferenceDisplay = getElement('weightDifference').getElementsByTagName('span')[0]; var estimatedWeeksDisplay = getElement('estimatedWeeks').getElementsByTagName('span')[0]; var weeklyCalorieAdjustmentDisplay = getElement('weeklyCalorieAdjustment').getElementsByTagName('span')[0]; var resultsSummaryTextDisplay = getElement('resultsSummaryText'); var currentWeightError = getElement('currentWeightError'); var goalWeightError = getElement('goalWeightError'); var weeklyRateError = getElement('weeklyRateError'); // Reset all error messages and styles [currentWeightError, goalWeightError, weeklyRateError].forEach(function(err) { err.style.display = 'none'; getElement(err.id.replace('Error', ")).style.borderColor = '#ccc'; }); // Input validation var isValidCurrentWeight = validateInput('currentWeight', 'currentWeightError', 1); var isValidGoalWeight = validateInput('goalWeight', 'goalWeightError', 1); var isValidWeeklyRate = validateInput('weeklyRate', 'weeklyRateError', -5, 5); // Allow rates from -5 to 5 if (!isValidCurrentWeight || !isValidGoalWeight || !isValidWeeklyRate) { resultsContainer.style.display = 'none'; return; } var currentWeight = parseFloat(currentWeightInput.value); var goalWeight = parseFloat(goalWeightInput.value); var weightUnit = weightUnitSelect.value; var weeklyRate = parseFloat(weeklyRateInput.value); var totalWeightDifference = Math.abs(goalWeight – currentWeight); var estimatedWeeks = 0; var weeklyCalorieAdjustment = 0; var changeDescription = "; var summaryClass = "; var caloriesPerUnit = (weightUnit === 'lbs') ? 3500 : 7700; if (weeklyRate === 0) { estimatedWeeks = Infinity; // Cannot reach goal if rate is 0 weeklyCalorieAdjustment = 0; changeDescription = "Rate cannot be zero for calculation."; } else { estimatedWeeks = totalWeightDifference / Math.abs(weeklyRate); weeklyCalorieAdjustment = (totalWeightDifference / estimatedWeeks) * caloriesPerUnit; if (goalWeight > currentWeight) { // Gaining weight weeklyCalorieAdjustment *= -1; // Surplus needed changeDescription = "You need to gain " + totalWeightDifference.toFixed(1) + " " + weightUnit + "."; summaryClass = 'positive-change'; } else { // Losing weight changeDescription = "You need to lose " + totalWeightDifference.toFixed(1) + " " + weightUnit + "."; summaryClass = 'negative-change'; } } var estimatedWeeksText = estimatedWeeks === Infinity ? "N/A" : estimatedWeeks.toFixed(2) + " weeks"; var weeklyCalorieAdjustmentText = weeklyCalorieAdjustment === 0 ? "N/A" : Math.abs(weeklyCalorieAdjustment).toFixed(0) + " " + (weeklyCalorieAdjustment > 0 ? "surplus" : "deficit") + "/week"; primaryResultDisplay.textContent = estimatedWeeksText; primaryResultDisplay.className = 'highlight'; if(estimatedWeeks !== Infinity && goalWeight > currentWeight) primaryResultDisplay.classList.add('positive-change'); if(estimatedWeeks !== Infinity && goalWeight currentWeight ? "surplus" : "deficit") + " of approximately " + Math.abs(weeklyCalorieAdjustment).toFixed(0) + " calories to reach your goal in roughly " + estimatedWeeks.toFixed(1) + " weeks."; resultsSummaryTextDisplay.className = 'results-summary ' + summaryClass; resultsContainer.style.display = 'block'; updateChartAndTable(currentWeight, goalWeight, weeklyRate, weightUnit, estimatedWeeks, totalWeightDifference); } function resetCalculator() { getElement('currentWeight').value = "; getElement('goalWeight').value = "; getElement('weightUnit').value = 'kg'; getElement('weeklyRate').value = "; getElement('currentWeightError').style.display = 'none'; getElement('goalWeightError').style.display = 'none'; getElement('weeklyRateError').style.display = 'none'; getElement('resultsContainer').style.display = 'none'; getElement('primaryResult').textContent = "; getElement('weightDifference').getElementsByTagName('span')[0].textContent = "; getElement('estimatedWeeks').getElementsByTagName('span')[0].textContent = "; getElement('weeklyCalorieAdjustment').getElementsByTagName('span')[0].textContent = "; getElement('resultsSummaryText').textContent = "; // Clear chart and table var ctx = getElement('weightChart').getContext('2d'); var chart = Chart.getChart(ctx); if (chart) chart.destroy(); getElement('milestoneTable').getElementsByTagName('tbody')[0].innerHTML = "; } function copyResults() { var primaryResult = getElement('primaryResult').innerText; var weightDifference = getElement('weightDifference').innerText.replace('Weight Difference', "); var estimatedWeeks = getElement('estimatedWeeks').innerText.replace('Estimated Weeks', "); var weeklyCalorieAdjustment = getElement('weeklyCalorieAdjustment').innerText.replace('Weekly Calorie Adjustment', "); var summary = getElement('resultsSummaryText').innerText; var textToCopy = "— Weight Transformation Results —\n\n"; textToCopy += "Primary Goal: " + primaryResult + "\n"; textToCopy += "Total Weight Change Needed: " + weightDifference.trim() + "\n"; textToCopy += "Estimated Time: " + estimatedWeeks.trim() + "\n"; textToCopy += "Weekly Calorie Adjustment: " + weeklyCalorieAdjustment.trim() + "\n\n"; textToCopy += "Summary: " + summary; navigator.clipboard.writeText(textToCopy).then(function() { var feedback = getElement('primaryResult').nextElementSibling.querySelector('.copy-feedback'); // Assuming feedback is near primary result if (!feedback) { feedback = document.createElement('span'); feedback.className = 'copy-feedback'; getElement('primaryResult').parentNode.insertBefore(feedback, getElement('primaryResult').nextSibling); } feedback.style.opacity = '1'; setTimeout(function() { feedback.style.opacity = '0'; }, 1500); }, function(err) { console.error('Could not copy text: ', err); var feedback = getElement('primaryResult').nextElementSibling.querySelector('.copy-feedback'); if (feedback) feedback.textContent = 'Copy Failed!'; if (feedback) feedback.style.opacity = '1'; setTimeout(function() { if (feedback) feedback.style.opacity = '0'; }, 1500); }); } // Charting logic using Chart.js (must be included separately or defined inline) // For this example, we'll use a simplified inline Chart.js definition. // NOTE: In a real-world scenario, you'd typically load Chart.js via a CDN or local file. // For this self-contained HTML, we'll assume Chart.js is available or define a minimal version if needed. // Since we cannot use external libraries, we'll simulate chart drawing with basic canvas API if Chart.js is not allowed. // However, the requirement specified "native OR pure SVG". Let's stick to canvas and assume Chart.js functionality is desired. // If Chart.js is strictly forbidden, a manual drawing approach would be needed, which is significantly more complex. // Let's use a placeholder for Chart.js functionality and explain it. // For a truly self-contained solution without external libs, we'd draw bars/lines manually. // Given the constraint "NO external chart libraries", and requirement for "dynamic chart", // a manual canvas drawing is the only pure native option. This is complex. // I will outline the manual drawing approach. var weightChartCanvas = getElement('weightChart'); var chartInstance = null; // To hold our manually drawn chart elements if needed function updateChartAndTable(currentWeight, goalWeight, weeklyRate, weightUnit, estimatedWeeks, totalWeightDifference) { var tbody = getElement('milestoneTable').getElementsByTagName('tbody')[0]; tbody.innerHTML = "; // Clear previous rows var ctx = weightChartCanvas.getContext('2d'); ctx.clearRect(0, 0, weightChartCanvas.width, weightChartCanvas.height); // Clear previous drawing if (estimatedWeeks === Infinity || !estimatedWeeks || estimatedWeeks > 100) { ctx.font = "16px Arial"; ctx.fillStyle = "#6c757d"; ctx.textAlign = "center"; ctx.fillText("Chart data not available for very long or infinite durations.", weightChartCanvas.width / 2, weightChartCanvas.height / 2); return; } var maxWeeksToShow = Math.min(estimatedWeeks, 52); // Show max 1 year or estimated weeks, whichever is less var numSteps = 20; var stepSize = maxWeeksToShow / numSteps; var dataPoints = []; var currentWeightForChart = currentWeight; var targetWeight = goalWeight; var isLosing = goalWeight < currentWeight; // Calculate data points for the chart and table for (var i = 0; i <= numSteps; i++) { var week = i * stepSize; var projectedWeight; var changeFromStart; if (weeklyRate === 0) { projectedWeight = currentWeight; } else { var actualChange = weeklyRate * week; projectedWeight = currentWeight + actualChange; changeFromStart = projectedWeight – currentWeight; } // Ensure projected weight doesn't overshoot target if calculating for gain, or undershoot if calculating for loss if (isLosing) { if (projectedWeight targetWeight) projectedWeight = targetWeight; } dataPoints.push({ week: week, projectedWeight: projectedWeight, changeFromStart: projectedWeight – currentWeight }); // Add to table if it's a significant milestone or end point if (i === 0 || i === numSteps || week % (Math.max(1, Math.floor(estimatedWeeks / 5))) === 0) { var row = tbody.insertRow(); var cellWeek = row.insertCell(0); var cellWeight = row.insertCell(1); var cellChangeFromStart = row.insertCell(2); var cellChangeUnits = row.insertCell(3); cellWeek.textContent = Math.round(week) === 0 ? "Start" : Math.round(week); cellWeight.textContent = projectedWeight.toFixed(1) + " " + weightUnit; cellChangeFromStart.textContent = changeFromStart.toFixed(1) + " " + weightUnit; cellChangeUnits.textContent = changeFromStart.toFixed(1); } } // Manually draw the chart on canvas var chartWidth = weightChartCanvas.width; var chartHeight = weightChartCanvas.height; var padding = 40; var chartAreaWidth = chartWidth – 2 * padding; var chartAreaHeight = chartHeight – 2 * padding; var minWeight = Math.min(currentWeight, targetWeight) – 5; var maxWeight = Math.max(currentWeight, targetWeight) + 5; var weightRange = maxWeight – minWeight; // Draw axes ctx.beginPath(); ctx.strokeStyle = '#ccc'; ctx.lineWidth = 1; // X-axis (Week) ctx.moveTo(padding, chartHeight – padding); ctx.lineTo(chartWidth – padding, chartHeight – padding); // Y-axis (Weight) ctx.moveTo(padding, padding); ctx.lineTo(padding, chartHeight – padding); ctx.stroke(); // Draw labels ctx.fillStyle = '#555'; ctx.font = "12px Arial"; ctx.textAlign = "center"; ctx.fillText("Weeks", chartWidth / 2, chartHeight – padding / 4); // X-axis label ctx.save(); ctx.translate(padding / 2, chartHeight / 2); ctx.rotate(-Math.PI / 2); ctx.fillText("Weight (" + weightUnit + ")", 0, 0); // Y-axis label ctx.restore(); // Draw scale ticks and labels // X-axis ticks for (var i = 0; i <= numSteps; i++) { var weekTick = i * stepSize; var xPos = padding + (weekTick / maxWeeksToShow) * chartAreaWidth; ctx.moveTo(xPos, chartHeight – padding); ctx.lineTo(xPos, chartHeight – padding + 5); if (i % 5 === 0 || i === numSteps) { // Label every 5 ticks or at the end ctx.fillText(Math.round(weekTick), xPos, chartHeight – padding + 15); } } // Y-axis ticks var numYTicks = 5; for (var i = 0; i <= numYTicks; i++) { var weightTickValue = minWeight + (i / numYTicks) * weightRange; var yPos = chartHeight – padding – ((weightTickValue – minWeight) / weightRange) * chartAreaHeight; ctx.moveTo(padding, yPos); ctx.lineTo(padding – 5, yPos); ctx.fillText(weightTickValue.toFixed(0), padding – 15, yPos + 5); } ctx.stroke(); // Draw the data series (Projected Weight) ctx.beginPath(); ctx.strokeStyle = '#004a99'; ctx.lineWidth = 2; var firstPoint = true; dataPoints.forEach(function(point) { var xPos = padding + (point.week / maxWeeksToShow) * chartAreaWidth; var yPos = chartHeight – padding – ((point.projectedWeight – minWeight) / weightRange) * chartAreaHeight; if (firstPoint) { ctx.moveTo(xPos, yPos); firstPoint = false; } else { ctx.lineTo(xPos, yPos); } ctx.stroke(); // Draw segment by segment for clarity }); // Draw current weight and goal weight markers // Current Weight marker var currentWeightY = chartHeight – padding – ((currentWeight – minWeight) / weightRange) * chartAreaHeight; ctx.beginPath(); ctx.strokeStyle = '#ffc107'; // Yellowish for current ctx.lineWidth = 2; ctx.moveTo(padding, currentWeightY); ctx.lineTo(chartWidth – padding, currentWeightY); ctx.stroke(); ctx.fillStyle = '#ffc107'; ctx.font = "12px Arial"; ctx.textAlign = "left"; ctx.fillText("Current (" + currentWeight.toFixed(1) + ")", padding + 5, currentWeightY – 5); // Goal Weight marker var goalWeightY = chartHeight – padding – ((targetWeight – minWeight) / weightRange) * chartAreaHeight; ctx.beginPath(); ctx.strokeStyle = '#28a745'; // Green for goal ctx.lineWidth = 2; ctx.moveTo(padding, goalWeightY); ctx.lineTo(chartWidth – padding, goalWeightY); ctx.stroke(); ctx.fillStyle = '#28a745'; ctx.font = "12px Arial"; ctx.textAlign = "left"; ctx.fillText("Goal (" + targetWeight.toFixed(1) + ")", padding + 5, goalWeightY – 5); // Add legend ctx.fillStyle = '#555'; ctx.font = "14px Arial"; ctx.textAlign = "center"; ctx.fillText("Projected Weight Trend", chartWidth / 2, padding / 2); } // Initial calculation on page load if inputs are pre-filled (optional) // Or just rely on user interaction. // Calling calculateWeight() here would require default values to be set.

Leave a Comment