Use this calculator to estimate your daily calorie needs for weight loss. It calculates your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and then suggests a calorie target based on your desired weekly weight loss.
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/physical job)
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function calculateCalories() {
var age = parseFloat(document.getElementById('age').value);
var gender = document.querySelector('input[name="gender"]:checked').value;
var height = parseFloat(document.getElementById('height').value);
var heightUnit = document.querySelector('input[name="heightUnit"]:checked').value;
var weight = parseFloat(document.getElementById('weight').value);
var weightUnit = document.querySelector('input[name="weightUnit"]:checked').value;
var activityLevelFactor = parseFloat(document.getElementById('activityLevel').value);
var weeklyWeightLoss = parseFloat(document.getElementById('weeklyWeightLoss').value);
var weeklyWeightLossUnit = document.querySelector('input[name="weeklyWeightLossUnit"]:checked').value;
var resultDiv = document.getElementById('result');
resultDiv.innerHTML = "; // Clear previous results
// Input validation
if (isNaN(age) || age <= 0 ||
isNaN(height) || height <= 0 ||
isNaN(weight) || weight <= 0 ||
isNaN(weeklyWeightLoss) || weeklyWeightLoss <= 0) {
resultDiv.innerHTML = 'Please enter valid positive numbers for all fields.';
return;
}
// Convert height to cm
var heightCm = height;
if (heightUnit === 'inches') {
heightCm = height * 2.54;
}
// Convert weight to kg
var weightKg = weight;
if (weightUnit === 'lbs') {
weightKg = weight / 2.20462;
}
// Convert weekly weight loss to kg
var weeklyWeightLossKg = weeklyWeightLoss;
if (weeklyWeightLossUnit === 'lbs') {
weeklyWeightLossKg = weeklyWeightLoss / 2.20462;
}
// Mifflin-St Jeor Equation for BMR
var bmr;
if (gender === 'male') {
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5;
} else { // female
bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161;
}
// Calculate TDEE (Total Daily Energy Expenditure)
var tdee = bmr * activityLevelFactor;
// Calculate daily calorie deficit for weight loss
// 1 kg of fat is approximately 7700 calories
var caloriesPerKgFat = 7700;
var totalWeeklyDeficit = weeklyWeightLossKg * caloriesPerKgFat;
var dailyDeficit = totalWeeklyDeficit / 7;
// Target calories for weight loss
var targetCalories = tdee – dailyDeficit;
// Display results
var warnings = [];
if (targetCalories < 1200 && gender === 'female') {
warnings.push('Warning: A daily intake below 1200 calories for women is generally not recommended without medical supervision.');
} else if (targetCalories 1) { // More than 1 kg (approx 2.2 lbs) per week
warnings.push('Warning: Losing more than 1 kg (2.2 lbs) per week can be difficult to sustain and may not be healthy for everyone. Consult a healthcare professional.');
}
var resultHtml = '
Your Calorie Needs for Weight Loss:
';
resultHtml += 'Your Basal Metabolic Rate (BMR): ' + bmr.toFixed(0) + ' calories/day';
resultHtml += 'Your Total Daily Energy Expenditure (TDEE): ' + tdee.toFixed(0) + ' calories/day';
resultHtml += 'To lose ' + weeklyWeightLoss.toFixed(1) + ' ' + weeklyWeightLossUnit + ' per week, you need a daily calorie deficit of approximately ' + dailyDeficit.toFixed(0) + ' calories.';
resultHtml += 'Your estimated daily calorie target for weight loss: ' + targetCalories.toFixed(0) + ' calories/day';
if (warnings.length > 0) {
resultHtml += '
';
for (var i = 0; i < warnings.length; i++) {
resultHtml += '' + warnings[i] + '';
}
resultHtml += '
';
}
resultDiv.innerHTML = resultHtml;
}
Understanding Your Calorie Needs for Weight Loss
Losing weight effectively and sustainably often comes down to creating a calorie deficit – consuming fewer calories than your body burns. This calculator helps you estimate this deficit based on several key factors.
What is a Calorie Deficit?
A calorie deficit occurs when you consistently consume fewer calories than your body expends. Your body then turns to stored energy (like fat) to make up the difference, leading to weight loss. A common guideline is that a deficit of 3500 calories equates to roughly one pound (0.45 kg) of fat loss. Therefore, a daily deficit of 500 calories aims for about one pound of weight loss per week.
Basal Metabolic Rate (BMR)
Your BMR is the number of calories your body needs to perform basic, life-sustaining functions while at rest. This includes breathing, circulation, cell production, nutrient processing, and maintaining body temperature. It's the minimum energy required to keep you alive. Our calculator uses the Mifflin-St Jeor equation, which is widely considered one of the most accurate BMR formulas.
Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: (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. To calculate TDEE, your BMR is multiplied by an activity factor:
Sedentary: Little or no exercise (BMR x 1.2)
Lightly Active: Light exercise/sports 1-3 days/week (BMR x 1.375)
Moderately Active: Moderate exercise/sports 3-5 days/week (BMR x 1.55)
Very Active: Hard exercise/sports 6-7 days a week (BMR x 1.725)
Extra Active: Very hard exercise/physical job (BMR x 1.9)
How to Use Your Calorie Target
Once you have your estimated daily calorie target for weight loss, you can use this number as a guide for your food intake. Remember that these are estimates, and individual results may vary. Factors like metabolism, body composition, and hormonal balance can influence your actual calorie needs.
Important Considerations for Healthy Weight Loss
Sustainable Deficit: Aim for a moderate calorie deficit (e.g., 250-1000 calories per day) to ensure sustainable and healthy weight loss. Rapid weight loss can lead to muscle loss, nutrient deficiencies, and rebound weight gain.
Nutrient Density: Focus on nutrient-dense foods like lean proteins, whole grains, fruits, vegetables, and healthy fats. These provide essential vitamins and minerals while keeping you feeling full.
Hydration: Drink plenty of water throughout the day. It can help with satiety and overall bodily functions.
Physical Activity: While diet is crucial for weight loss, regular physical activity complements your efforts by burning additional calories, building muscle, and improving overall health.
Listen to Your Body: Pay attention to hunger cues and energy levels. If you feel constantly fatigued or excessively hungry, your calorie target might be too low.
Consult a Professional: For personalized advice, especially if you have underlying health conditions or specific dietary needs, consult a doctor, registered dietitian, or certified nutritionist.
This calculator provides a helpful starting point for your weight loss journey. Combine this knowledge with a balanced diet and regular exercise for the best results.