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/week)
Extra Active (very hard exercise/physical job)
0.5 lbs per week
1 lb per week
1.5 lbs per week
2 lbs per week
A safe and sustainable rate is typically 1-2 lbs per week.
Your Calorie Deficit Plan
Your Basal Metabolic Rate (BMR): calories/day
Your Total Daily Energy Expenditure (TDEE): calories/day
Daily Calorie Deficit for Goal: calories/day
Your Target Daily Calorie Intake: calories/day
function calculateCalorieDeficit() {
var genderMale = document.getElementById('genderMale').checked;
var age = parseFloat(document.getElementById('age').value);
var weightLbs = parseFloat(document.getElementById('weight').value);
var heightFeet = parseFloat(document.getElementById('heightFeet').value);
var heightInches = parseFloat(document.getElementById('heightInches').value);
var activityLevel = document.getElementById('activityLevel').value;
var weightLossGoalLbs = parseFloat(document.getElementById('weightLossGoal').value);
var errorMessageDiv = document.getElementById('errorMessage');
var resultDiv = document.getElementById('result');
errorMessageDiv.style.display = 'none';
resultDiv.style.display = 'none';
// Input validation
if (isNaN(age) || age <= 0 || isNaN(weightLbs) || weightLbs <= 0 || isNaN(heightFeet) || heightFeet < 0 || isNaN(heightInches) || heightInches 11) {
errorMessageDiv.textContent = 'Please enter valid positive numbers for all fields (Age, Weight, Height).';
errorMessageDiv.style.display = 'block';
return;
}
// Convert weight to kg
var weightKg = weightLbs / 2.20462;
// Convert height to cm
var totalHeightInches = (heightFeet * 12) + heightInches;
var heightCm = totalHeightInches * 2.54;
var bmr;
// Mifflin-St Jeor Equation
if (genderMale) {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else { // Female
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161;
}
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 = 1.55; // Default to moderately active
}
var tdee = bmr * activityFactor;
// 1 lb of fat is approximately 3500 calories
// Daily deficit = (weekly goal in lbs * 3500) / 7 days
var dailyCalorieDeficit = (weightLossGoalLbs * 3500) / 7;
var targetDailyCalorieIntake = tdee – dailyCalorieDeficit;
// Ensure target intake doesn't go too low (e.g., below 1200 for women, 1500 for men)
var minRecommendedCalories = genderMale ? 1500 : 1200;
if (targetDailyCalorieIntake < minRecommendedCalories) {
errorMessageDiv.textContent = 'Warning: Your calculated target intake of ' + Math.round(targetDailyCalorieIntake) + ' calories is very low. It is generally not recommended to go below ' + minRecommendedCalories + ' calories per day without medical supervision. Consider a slower weight loss goal.';
errorMessageDiv.style.display = 'block';
targetDailyCalorieIntake = minRecommendedCalories; // Cap at minimum for display
}
document.getElementById('bmrResult').textContent = Math.round(bmr);
document.getElementById('tdeeResult').textContent = Math.round(tdee);
document.getElementById('deficitResult').textContent = Math.round(dailyCalorieDeficit);
document.getElementById('targetCaloriesResult').textContent = Math.round(targetDailyCalorieIntake);
resultDiv.style.display = 'block';
}
Understanding the Calorie Deficit for Weight Loss
Achieving sustainable weight loss often boils down to one fundamental principle: creating a calorie deficit. This means consistently consuming fewer calories than your body expends. Our Calorie Deficit Calculator helps you determine the ideal daily calorie intake to reach your weight loss goals safely and effectively.
What is a Calorie Deficit?
A calorie deficit occurs when you burn more calories than you consume. Your body needs a certain amount of energy (calories) to perform its basic functions, like breathing and circulation (Basal Metabolic Rate or BMR), and additional energy for physical activity. When you don't provide enough calories through food, your body turns to stored energy, primarily fat, to make up the difference, leading to weight loss.
How Our Calculator Works
Our calculator uses a multi-step approach to give you a personalized calorie deficit plan:
Basal Metabolic Rate (BMR): This is the number of calories your body burns at rest to maintain vital functions. We use the widely accepted Mifflin-St Jeor equation, which considers your gender, age, weight, and height for an accurate estimate.
Total Daily Energy Expenditure (TDEE): Your TDEE is your BMR plus the calories you burn through physical activity. We factor in your chosen activity level (sedentary, lightly active, moderately active, very active, or extra active) to estimate your total daily calorie burn.
Desired Calorie Deficit: To lose weight, you need to create a deficit. Since approximately 3,500 calories equate to one pound of body fat, a daily deficit of 500 calories typically leads to a loss of one pound per week (500 calories/day * 7 days/week = 3,500 calories/week). You select your desired weekly weight loss, and the calculator determines the necessary daily deficit.
Target Daily Calorie Intake: Finally, we subtract your daily calorie deficit from your TDEE to provide your target daily calorie intake for weight loss.
Safe and Sustainable Weight Loss
While it might be tempting to aim for a large calorie deficit to lose weight quickly, a gradual and sustainable approach is generally healthier and more effective in the long run. Most health professionals recommend a weight loss rate of 1 to 2 pounds per week. This allows your body to adapt, minimizes muscle loss, and is easier to maintain.
Extreme calorie restriction can lead to nutrient deficiencies, fatigue, muscle loss, and can even slow down your metabolism, making future weight loss more challenging. Our calculator provides a warning if your target calorie intake falls below generally recommended minimums (e.g., 1200 for women, 1500 for men) to encourage a healthier approach.
Tips for Achieving Your 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 on fewer calories.
Portion Control: Be mindful of serving sizes. Even healthy foods can contribute to a calorie surplus if consumed in excess.
Increase Physical Activity: While diet is key, increasing your activity level helps burn more calories, contributing to your deficit and improving overall health.
Stay Hydrated: Drinking plenty of water can help you feel full and may boost your metabolism.
Track Your Intake: Using a food diary or a calorie-tracking app can help you stay accountable and aware of your daily calorie consumption.
Get Enough Sleep: Poor sleep can disrupt hormones that regulate appetite, making it harder to stick to a calorie deficit.
Disclaimer: This calculator provides an estimate based on standard formulas. Individual metabolic rates and calorie needs can vary. It is always recommended to consult with a healthcare professional or a registered dietitian before making significant changes to your diet or exercise routine, especially if you have underlying health conditions.