Sedentary (little or no exercise)
Lightly Active (light exercise/sports 1-3 days/week)
Moderately Active (moderate exercise/sports 3-5 days/week)
Very Active (hard exercise/sports 6-7 days a week)
Extra Active (very hard exercise/sports & physical job)
Your Weight Loss Plan
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Estimated Daily Caloric Intake for Goal
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Required Weekly Calorie Deficit
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Estimated Time to Reach Goal
Understanding Calorie Deficit for Effective Weight Loss
Losing weight sustainably is fundamentally about creating a calorie deficit – consuming fewer calories than your body burns. This calculator helps you estimate your daily caloric needs to achieve a specific weight loss goal, providing a roadmap for a healthier you.
The Science Behind the Calculation
To calculate your calorie deficit, we first need to estimate your Basal Metabolic Rate (BMR) and then your Total Daily Energy Expenditure (TDEE).
Basal Metabolic Rate (BMR): This is the number of calories your body needs to perform basic life-sustaining functions at rest. We use the Mifflin-St Jeor equation, which is considered one of the most 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
Total Daily Energy Expenditure (TDEE): This is your BMR multiplied by an activity factor that reflects your lifestyle. It represents the total calories you burn in a day.
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
Calorie Deficit for Weight Loss: A deficit of approximately 3,500 calories is needed to lose one pound (0.45 kg) of fat. To lose 1 kg of fat, a deficit of about 7,700 calories is required. We use this principle to determine your target daily intake and time to reach your goal.
Target Daily Calorie Intake = TDEE – (Target Weekly Loss in kg × 7700 kcal / 7 days)
Weekly Calorie Deficit = Target Weekly Loss in kg × 7700 kcal
Estimated Time to Goal (weeks) = (Current Weight – Goal Weight) / Target Weekly Loss
How to Use This Calculator
Enter Current Details: Input your current weight, height, age, and gender.
Select Activity Level: Choose the option that best describes your average daily physical activity.
Set Your Goal: Enter your desired goal weight and how much weight you aim to lose per week (0.1 kg to 2 kg is generally considered safe and sustainable).
Calculate: Click the 'Calculate' button.
The calculator will provide your estimated daily calorie intake to achieve your goal, the total weekly deficit needed, and an estimated timeframe to reach your target weight.
Important Considerations
Consult a Professional: This calculator provides estimates. Always consult with a doctor or registered dietitian before making significant changes to your diet or exercise routine, especially if you have underlying health conditions.
Nutrient Density: Focus on consuming nutrient-dense foods (fruits, vegetables, lean proteins, whole grains) to ensure you're meeting your nutritional needs while in a calorie deficit.
Sustainability: Aim for a moderate weight loss rate (0.5-1 kg per week) for sustainable results and better health outcomes. Rapid weight loss can be detrimental.
Listen to Your Body: Pay attention to hunger cues, energy levels, and overall well-being. Adjust your intake and activity as needed.
Muscle vs. Fat: Weight loss is not solely fat loss. Changes in body composition can affect the number on the scale. Consider tracking other metrics like body measurements.
function calculateCalorieDeficit() {
var currentWeight = parseFloat(document.getElementById("currentWeight").value);
var height = parseFloat(document.getElementById("height").value);
var age = parseInt(document.getElementById("age").value);
var gender = document.getElementById("gender").value;
var activityLevel = parseFloat(document.getElementById("activityLevel").value);
var goalWeight = parseFloat(document.getElementById("goalWeight").value);
var lossRate = parseFloat(document.getElementById("lossRate").value);
var errorMessage = "";
if (isNaN(currentWeight) || currentWeight <= 0) {
errorMessage += "Please enter a valid current weight.\n";
}
if (isNaN(height) || height <= 0) {
errorMessage += "Please enter a valid height.\n";
}
if (isNaN(age) || age <= 0) {
errorMessage += "Please enter a valid age.\n";
}
if (isNaN(goalWeight) || goalWeight = currentWeight) {
errorMessage += "Goal weight must be less than current weight for weight loss.\n";
}
if (isNaN(lossRate) || lossRate 2) {
errorMessage += "Please enter a target weekly loss rate between 0.1 kg and 2 kg.\n";
}
if (errorMessage !== "") {
alert(errorMessage);
document.getElementById("result-section").style.display = 'none';
return;
}
// Calculate BMR (Mifflin-St Jeor Equation)
var bmr;
if (gender === "male") {
bmr = (10 * currentWeight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * currentWeight) + (6.25 * height) – (5 * age) – 161;
}
// Calculate TDEE
var tdee = bmr * activityLevel;
// Constants
var kcalPerKgFat = 7700; // Approximate calories in 1 kg of fat
// Calculate required weekly deficit
var weeklyDeficit = lossRate * kcalPerKgFat;
// Calculate target daily calorie intake
var dailyCalorieIntake = tdee – (weeklyDeficit / 7);
// Ensure daily intake is not too low (e.g., below BMR or a safe minimum)
var safeMinDailyIntake = 1200; // General safe minimum for women, 1500 for men could also be a consideration
if (gender === 'male' && dailyCalorieIntake < 1500) {
dailyCalorieIntake = 1500;
} else if (dailyCalorieIntake < safeMinDailyIntake) {
dailyCalorieIntake = safeMinDailyIntake;
}
// Recalculate weekly deficit and loss rate if daily intake was adjusted upwards to minimums
var adjustedWeeklyDeficit = tdee – dailyCalorieIntake;
var adjustedLossRate = adjustedWeeklyDeficit / kcalPerKgFat;
// Calculate time to reach goal
var weightDifference = currentWeight – goalWeight;
var timeToGoalWeeks = weightDifference / adjustedLossRate; // Use adjusted loss rate if daily intake was capped
// Display results
document.getElementById("dailyCalories").innerText = Math.round(dailyCalorieIntake);
document.getElementById("weeklyDeficit").innerText = Math.round(adjustedWeeklyDeficit);
document.getElementById("timeToGoal").innerText = timeToGoalWeeks.toFixed(1) + " weeks";
document.getElementById("result-section").style.display = 'block';
}