Calculate your daily calorie needs for muscle gain, maintenance, or fat loss.
Male
Female
Sedentary (little to 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)
Muscle Gain (Surplus)
Maintenance
Fat Loss (Deficit)
Your Estimated Daily Calories:
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Understanding Your Calorie Needs for Bodybuilding
Achieving your bodybuilding goals, whether it's building lean muscle mass, maintaining your physique, or shedding body fat, hinges on precise caloric intake. A calorie calculator for bodybuilding is an essential tool that helps estimate your Total Daily Energy Expenditure (TDEE) and then adjusts it based on your specific objectives. This ensures you're fueling your body correctly for optimal results.
How the Calculator Works: Basal Metabolic Rate (BMR)
At the core of most calorie calculators is the Basal Metabolic Rate (BMR). This is the number of calories your body burns at rest to maintain basic life-sustaining functions like breathing, circulation, and cell production. The most commonly used formulas for BMR are the Harris-Benedict Equation and the Mifflin-St Jeor Equation. This calculator uses a variation of the Mifflin-St Jeor Equation, which is generally considered more accurate for modern populations:
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
Adjusting for Activity Level: TDEE
Your BMR represents your caloric needs at complete rest. To find your Total Daily Energy Expenditure (TDEE) – the total calories you burn in a day, including all activities – your BMR is multiplied by an Activity Factor:
Very Active: BMR × 1.725 (hard exercise/sports 6-7 days a week)
Extra Active: BMR × 1.9 (very hard exercise/sports & physical job)
Calorie Goals: Surplus, Maintenance, or Deficit
Once your TDEE is calculated, it's adjusted based on your bodybuilding goal:
Muscle Gain: To build muscle, you need to consume more calories than you burn (a caloric surplus). Typically, a surplus of 250-500 calories above your TDEE is recommended to promote muscle growth while minimizing excessive fat gain.
Maintenance: To maintain your current weight and physique, your calorie intake should match your TDEE.
Fat Loss: To lose fat, you need to consume fewer calories than you burn (a caloric deficit). A deficit of 250-500 calories below your TDEE is generally recommended for sustainable fat loss without significant muscle loss.
Note: These are estimates. Individual metabolisms can vary, and it's crucial to monitor your progress and adjust your intake as needed. This calculator provides a starting point for tailoring your nutrition to your bodybuilding journey.
function calculateCalories() {
var weight = parseFloat(document.getElementById("weight").value);
var height = parseFloat(document.getElementById("height").value);
var age = parseFloat(document.getElementById("age").value);
var gender = document.getElementById("gender").value;
var activityLevel = document.getElementById("activityLevel").value;
var goal = document.getElementById("goal").value;
var bmr = 0;
var tdee = 0;
var finalCalories = 0;
var goalDescription = "";
// Validate inputs
if (isNaN(weight) || isNaN(height) || isNaN(age) || weight <= 0 || height <= 0 || age <= 0) {
document.getElementById("result-value").innerText = "Invalid Input";
document.getElementById("goal-description").innerText = "Please enter valid positive numbers for weight, height, and age.";
return;
}
// Calculate BMR (Mifflin-St Jeor Equation)
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// Determine activity factor
var activityFactor = 0;
switch (activityLevel) {
case "sedentary":
activityFactor = 1.2;
break;
case "light":
activityFactor = 1.375;
break;
case "moderate":
activityFactor = 1.55;
break;
case "veryActive":
activityFactor = 1.725;
break;
case "extraActive":
activityFactor = 1.9;
break;
}
// Calculate TDEE
tdee = bmr * activityFactor;
// Adjust for goal
var calorieAdjustment = 0;
switch (goal) {
case "muscleGain":
calorieAdjustment = 300; // Approx +300-500 kcal surplus
goalDescription = "Aiming for muscle gain. A slight calorie surplus is needed.";
break;
case "maintenance":
calorieAdjustment = 0;
goalDescription = "Aiming for maintenance. Your calories should match your TDEE.";
break;
case "fatLoss":
calorieAdjustment = -300; // Approx -300-500 kcal deficit
goalDescription = "Aiming for fat loss. A moderate calorie deficit is recommended.";
break;
}
finalCalories = tdee + calorieAdjustment;
// Ensure final calories are not unrealistically low (e.g., below BMR for fat loss)
if (goal === "fatLoss" && finalCalories < bmr * 0.8) { // Prevent overly aggressive deficits
finalCalories = bmr * 0.8;
goalDescription += " (Adjusted to prevent an overly aggressive deficit.)";
} else if (finalCalories < 1200 && gender === "female") { // Minimum for females
finalCalories = 1200;
goalDescription += " (Adjusted to a minimum of 1200 kcal.)";
} else if (finalCalories < 1500 && gender === "male") { // Minimum for males
finalCalories = 1500;
goalDescription += " (Adjusted to a minimum of 1500 kcal.)";
}
document.getElementById("result-value").innerText = Math.round(finalCalories) + " kcal";
document.getElementById("goal-description").innerText = goalDescription;
}