Free Calorie Deficit Calculator
Use this calculator to estimate your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and the daily calorie intake needed to achieve your desired weight loss goal.
Understanding Your Calorie Deficit
A calorie deficit is the foundation of weight loss. It occurs when you consistently consume fewer calories than your body burns. When your body doesn't get enough energy from food, it starts to use stored fat for fuel, leading to weight reduction.
How the Calculator Works:
This calculator uses a multi-step approach to help you determine your optimal calorie intake for weight loss:
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Basal Metabolic Rate (BMR): Your BMR is the number of calories your body needs to perform basic, life-sustaining functions while at rest (e.g., breathing, circulation, cell production). We use the Mifflin-St Jeor equation, which is widely recognized for its accuracy:
- 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
-
Total Daily Energy Expenditure (TDEE): Your TDEE is the total number of calories your body burns in a 24-hour period, including your BMR and the calories expended through physical activity. Your BMR is multiplied by an activity factor based on your lifestyle:
- Sedentary: BMR × 1.2 (little or no exercise)
- Lightly Active: BMR × 1.375 (light exercise/sports 1-3 days/week)
- Moderately Active: BMR × 1.55 (moderate exercise/sports 3-5 days/week)
- Very Active: BMR × 1.725 (hard exercise/sports 6-7 days a week)
- Extra Active: BMR × 1.9 (very hard exercise/physical job/training twice a day)
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Calorie Deficit for Weight Loss: To lose weight, you need to create a deficit. Approximately 7,700 calories need to be burned to lose 1 kilogram of body fat. The calculator determines the daily deficit required to meet your desired weekly weight loss goal. For example, to lose 0.5 kg per week, you need a daily deficit of about 550 calories (3850 calories / 7 days).
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Target Daily Calorie Intake: Finally, your target daily calorie intake is calculated by subtracting your daily calorie deficit from your TDEE. This is the estimated number of calories you should aim to consume each day to achieve your weight loss goal.
Tips for Achieving a Healthy Calorie Deficit:
- Focus on Nutrient-Dense Foods: Prioritize whole foods like lean proteins, fruits, vegetables, and whole grains. They provide essential nutrients and keep you feeling full.
- Increase Physical Activity: Exercise helps burn more calories, contributing to your deficit. Combine cardiovascular workouts with strength training.
- Stay Hydrated: Drinking plenty of water can help manage hunger and boost metabolism.
- Monitor Portions: Even healthy foods can contribute to excess calories if consumed in large quantities.
- Be Patient and Consistent: Sustainable weight loss takes time. Aim for a gradual, steady loss of 0.5-1 kg (1-2 lbs) per week.
- Listen to Your Body: If you feel excessively hungry or fatigued, you might be in too large of a deficit. Adjust your intake slightly.
Disclaimer: This calculator provides an estimate and should not replace professional medical or nutritional advice. Consult with a healthcare provider or registered dietitian before making significant changes to your diet or exercise routine.
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function calculateCalorieDeficit() {
// Get input values
var gender = document.getElementById("gender").value;
var age = parseFloat(document.getElementById("age").value);
var weight = parseFloat(document.getElementById("weight").value); // kg
var height = parseFloat(document.getElementById("height").value); // cm
var activityLevel = document.getElementById("activityLevel").value;
var desiredLossKg = parseFloat(document.getElementById("desiredLossKg").value); // kg per week
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(age) || age <= 0 ||
isNaN(weight) || weight <= 0 ||
isNaN(height) || height <= 0 ||
isNaN(desiredLossKg) || desiredLossKg <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Step 1: Calculate BMR (Basal Metabolic Rate) using Mifflin-St Jeor equation
var bmr;
if (gender === 'male') {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// Step 2: Calculate TDEE (Total Daily Energy Expenditure)
var activityFactor;
switch (activityLevel) {
case 'sedentary':
activityFactor = 1.2;
break;
case 'lightlyActive':
activityFactor = 1.375;
break;
case 'moderatelyActive':
activityFactor = 1.55;
break;
case 'veryActive':
activityFactor = 1.725;
break;
case 'extraActive':
activityFactor = 1.9;
break;
default:
activityFactor = 1.2; // Default to sedentary if somehow invalid
}
var tdee = bmr * activityFactor;
// Step 3: Calculate Daily Calorie Deficit for desired weight loss
// Approximately 7700 calories per 1 kg of fat
var caloriesPerKgFat = 7700;
var totalWeeklyDeficit = desiredLossKg * caloriesPerKgFat;
var dailyDeficit = totalWeeklyDeficit / 7;
// Step 4: Calculate Target Daily Calorie Intake
var targetCalories = tdee – dailyDeficit;
// Ensure target calories don't go too low for health reasons (e.g., below 1200 for women, 1500 for men)
// This is a simplified check; actual minimums depend on individual factors.
var minRecommendedCalories = (gender === 'male') ? 1500 : 1200;
if (targetCalories < minRecommendedCalories) {
resultDiv.innerHTML += "
Warning: Your calculated target daily calorie intake (" + targetCalories.toFixed(0) + " kcal) is below the generally recommended minimum for healthy adults (" + minRecommendedCalories + " kcal). A larger deficit might be unhealthy. Consider reducing your desired weekly weight loss or consulting a professional.";
targetCalories = minRecommendedCalories; // Cap at minimum for display purposes, but warn user
}
// Display results
resultDiv.innerHTML += "Your estimated
Basal Metabolic Rate (BMR): " + bmr.toFixed(0) + " kcal/day";
resultDiv.innerHTML += "Your estimated
Total Daily Energy Expenditure (TDEE): " + tdee.toFixed(0) + " kcal/day";
resultDiv.innerHTML += "To lose
" + desiredLossKg.toFixed(1) + " kg per week, you need a daily calorie deficit of approximately
" + dailyDeficit.toFixed(0) + " kcal/day.";
resultDiv.innerHTML += "Your
Target Daily Calorie Intake for this goal is:
" + targetCalories.toFixed(0) + " kcal/day";
resultDiv.innerHTML += "
Remember to consult with a healthcare professional or registered dietitian for personalized advice.";
}