Estimate your MET value (Metabolic Equivalent of Task). Sedentary (sitting, lying) ~1.375, Light activity (standing, walking slowly) ~2.5, Moderate activity (moderate exercise) ~5.0, Heavy activity (vigorous exercise) ~7.5. Consult resources for precise values.
Revised Harris-Benedict
Mifflin-St Jeor
Male
Female
Your Calorie Deficit Plan
Understanding Calorie Deficit for Effective Weight Loss
Losing weight sustainably primarily involves creating a calorie deficit. This means consuming fewer calories than your body expends. Your body needs a certain amount of energy (calories) to function daily, which is determined by your Basal Metabolic Rate (BMR) and your activity level. By understanding these components, you can strategically reduce your calorie intake to achieve your weight loss goals.
What is a Calorie Deficit?
A calorie is a unit of energy. When you eat, you consume calories. When you exercise or perform daily activities, you burn calories. A calorie deficit occurs when your energy expenditure exceeds your energy intake. For every pound of fat you aim to lose, you need to create a deficit of approximately 3,500 calories. This calculator helps you determine the daily calorie deficit needed to reach your desired weight loss at a healthy pace.
Key Components of Calorie Expenditure
Basal Metabolic Rate (BMR): This is the number of calories your body burns at rest to maintain basic life functions like breathing, circulation, and cell production. Factors like age, gender, weight, and height influence BMR.
Total Daily Energy Expenditure (TDEE): This is the total number of calories you burn in a day, including your BMR and calories burned through physical activity (exercise and non-exercise activity thermogenesis – NEAT).
How the Calculator Works
This calculator estimates your TDEE and then determines the necessary daily calorie deficit based on your weight loss goals.
BMR Calculation: It uses either the Revised Harris-Benedict or Mifflin-St Jeor equation, which are widely accepted formulas for estimating BMR.
Revised Harris-Benedict (1990):
Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age in years)
Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age in years)
Mifflin-St Jeor (1990):
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
TDEE Calculation: Your BMR is multiplied by an activity factor derived from your input activity level (METs). While METs are primarily used for exercise, we use a simplified approach to infer an overall activity multiplier. A rough approximation is often used where:
Sedentary (little to no exercise): BMR × 1.2
Lightly active (light exercise/sports 1-3 days/week): BMR × 1.375
Moderately active (moderate exercise/sports 3-5 days/week): BMR × 1.55
Very active (hard exercise/sports 6-7 days a week): BMR × 1.725
Extra active (very hard exercise/sports & physical job): BMR × 1.9
Note: The calculator uses a direct MET value for simplicity, but accurate TDEE with METs involves more complex calculations factoring in duration and intensity. The provided MET input serves as an approximate multiplier.
Weight Loss Calculation: The total weight to lose is calculated (Current Weight – Goal Weight). This total weight loss is then divided by the desired weekly loss to determine the number of weeks needed. The total calorie deficit required is (Total Weight Loss in kg × 7700) – assuming 7700 calories per kg of fat. This total deficit is then divided by the number of weeks to find the average daily calorie deficit.
How to Use the Calculator
Enter your current weight, goal weight, desired weekly weight loss rate, and your estimated activity level. You'll also need to input your age, height, and select your gender. The calculator will provide an estimated daily calorie deficit required to achieve your goal.
Important Considerations
Sustainability: Aim for a safe and sustainable weekly weight loss of 0.5 kg to 1 kg (approximately 1-2 pounds). Aggressive weight loss can be unhealthy and difficult to maintain.
Nutrition: Focus on a balanced diet rich in whole foods. A calorie deficit should not mean a nutrient deficit.
Exercise: Regular physical activity not only burns calories but also improves overall health, builds muscle, and boosts metabolism.
Consult Professionals: Always consult with a healthcare provider or a registered dietitian before making significant changes to your diet or exercise routine, especially if you have underlying health conditions.
Accuracy: Calorie expenditure estimations are approximations. Individual metabolisms can vary. Adjust your intake and monitor your progress accordingly.
function calculateCalorieDeficit() {
var currentWeight = parseFloat(document.getElementById("currentWeight").value);
var goalWeight = parseFloat(document.getElementById("goalWeight").value);
var weeklyWeightLossGoal = parseFloat(document.getElementById("weeklyWeightLossGoal").value);
var currentActivityLevel = parseFloat(document.getElementById("currentActivityLevel").value);
var bmrMethod = document.getElementById("bmrMethod").value;
var age = parseFloat(document.getElementById("age").value);
var heightCm = parseFloat(document.getElementById("heightCm").value);
var gender = document.getElementById("gender").value;
var resultMessageElement = document.getElementById("result-message");
var resultValueElement = document.getElementById("result-value");
resultMessageElement.innerText = "";
resultValueElement.innerText = "";
// Input validation
if (isNaN(currentWeight) || currentWeight <= 0 ||
isNaN(goalWeight) || goalWeight <= 0 ||
isNaN(weeklyWeightLossGoal) || weeklyWeightLossGoal <= 0 ||
isNaN(currentActivityLevel) || currentActivityLevel <= 0 ||
isNaN(age) || age <= 0 ||
isNaN(heightCm) || heightCm = currentWeight) {
resultMessageElement.innerText = "Your goal weight should be less than your current weight for weight loss.";
return;
}
var bmr = 0;
// BMR Calculation
if (bmrMethod === "harris-benedict") {
if (gender === "male") {
bmr = 88.362 + (13.397 * currentWeight) + (4.799 * heightCm) – (5.677 * age);
} else { // female
bmr = 447.593 + (9.247 * currentWeight) + (3.098 * heightCm) – (4.330 * age);
}
} else { // mifflin-st-jeor
if (gender === "male") {
bmr = (10 * currentWeight) + (6.25 * heightCm) – (5 * age) + 5;
} else { // female
bmr = (10 * currentWeight) + (6.25 * heightCm) – (5 * age) – 161;
}
}
// TDEE Calculation – Simplified multiplier approach using the provided activity level MET value.
// A direct MET value is less common for TDEE calculation without duration/intensity.
// This interprets the MET value as a direct multiplier for simplicity.
// For more accuracy, one would typically use standard activity factors (1.2, 1.375, etc.)
// or calculate specific activity calorie burn and add it to BMR.
// Using the provided MET value directly as a multiplier for TDEE.
var tdee = bmr * currentActivityLevel;
// Weight Loss Calculation
var totalWeightLossKg = currentWeight – goalWeight;
// Approximate calories in 1 kg of fat is 7700 kcal
var totalCalorieDeficitRequired = totalWeightLossKg * 7700;
var weeksToGoal = totalWeightLossKg / weeklyWeightLossGoal;
// Ensure weeksToGoal is not zero or negative to avoid division by zero
if (weeksToGoal <= 0) {
resultMessageElement.innerText = "Cannot calculate weeks to goal with the given inputs.";
return;
}
var dailyCalorieDeficit = totalCalorieDeficitRequired / (weeksToGoal * 7); // Divide by days in weeks
// Ensure daily deficit is not excessively large or negative
if (dailyCalorieDeficit <= 0) {
resultMessageElement.innerText = "Your inputs result in no calorie deficit required or a surplus.";
return;
}
// Calculate target daily calorie intake
var targetDailyIntake = tdee – dailyCalorieDeficit;
if (targetDailyIntake <= 0) {
resultMessageElement.innerText = "Based on your inputs, your target daily intake would be zero or negative, which is not healthy. Please adjust your goals or activity level.";
return;
}
var formattedDailyDeficit = dailyCalorieDeficit.toFixed(0);
var formattedTargetIntake = targetDailyIntake.toFixed(0);
var formattedWeeksToGoal = weeksToGoal.toFixed(1);
resultMessageElement.innerHTML =
"To lose " + totalWeightLossKg.toFixed(1) + " kg at a rate of " + weeklyWeightLossGoal + " kg per week, it will take approximately " + formattedWeeksToGoal + " weeks." +
"Your estimated TDEE (Total Daily Energy Expenditure) is: " + tdee.toFixed(0) + " calories/day." +
"To achieve this, aim for a daily calorie deficit of approximately: " + formattedDailyDeficit + " calories/day." +
"This means your target daily calorie intake should be around: " + formattedTargetIntake + " calories/day.";
resultValueElement.innerHTML = formattedDailyDeficit + " kcal/day";
}