Use this calculator to estimate your daily calorie needs and macronutrient breakdown (protein, fat, carbohydrates) based on your personal data and activity level. This can be a great starting point for managing your diet for weight loss, maintenance, or gain.
lbs
kg
inches
cm
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/training twice a day)
Maintain Weight
Mild Weight Loss (0.5 lbs/week)
Moderate Weight Loss (1 lbs/week)
Extreme Weight Loss (2 lbs/week)
Mild Weight Gain (0.5 lbs/week)
Moderate Weight Gain (1 lbs/week)
Extreme Weight Gain (2 lbs/week)
Understanding Calories and Macronutrients
Calories are units of energy that your body uses to perform all its functions, from breathing and thinking to exercising. Macronutrients, or "macros," are the three main types of nutrients that provide these calories: protein, fats, and carbohydrates. Each plays a vital role in your health and body composition.
Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE)
Basal Metabolic Rate (BMR): This is the number of calories your body burns at rest to maintain basic bodily functions like breathing, circulation, and cell production. It's the minimum energy required to keep you alive.
Total Daily Energy Expenditure (TDEE): This is your BMR plus the calories you burn through physical activity, digestion, and other daily movements. It represents the total number of calories your body expends in a 24-hour period.
The Role of Macronutrients
Protein (4 calories per gram): Essential for building and repairing tissues, making enzymes and hormones, and supporting immune function. It's crucial for muscle growth and recovery.
Fats (9 calories per gram): Important for hormone production, nutrient absorption, cell membrane structure, and providing a concentrated source of energy. Healthy fats are vital for overall health.
Carbohydrates (4 calories per gram): The body's primary source of energy. They fuel your brain, muscles, and central nervous system. Carbs are broken down into glucose, which is used immediately or stored as glycogen.
How to Use This Calculator
Enter Your Age, Gender, Weight, and Height: Provide accurate information as these are fundamental to calculating your BMR.
Select Your Activity Level: Choose the option that best describes your typical weekly exercise routine. Be honest for the most accurate TDEE.
Choose Your Goal: Whether you want to maintain your current weight, lose weight, or gain weight, this selection will adjust your target calorie intake accordingly.
Click "Calculate Macros": The calculator will then provide your estimated BMR, TDEE, target daily calories, and a breakdown of recommended protein, fat, and carbohydrate intake in both grams and calories.
Interpreting Your Results
The results provide a starting point for your dietary planning. For weight loss, a calorie deficit (eating fewer calories than your TDEE) is necessary. For weight gain, a calorie surplus (eating more than your TDEE) is needed. Macronutrient ratios can be adjusted based on personal preference, dietary needs, and specific fitness goals (e.g., higher protein for muscle building). Always listen to your body and adjust as needed.
Disclaimer: This calculator provides estimates 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 calculateMacros() {
var age = parseFloat(document.getElementById('age').value);
var gender = document.querySelector('input[name="gender"]:checked').value;
var weight = parseFloat(document.getElementById('weight').value);
var weightUnit = document.getElementById('weightUnit').value;
var height = parseFloat(document.getElementById('height').value);
var heightUnit = document.getElementById('heightUnit').value;
var activityFactor = parseFloat(document.getElementById('activityLevel').value);
var goal = document.getElementById('goal').value;
// Input validation
if (isNaN(age) || age <= 0 || isNaN(weight) || weight <= 0 || isNaN(height) || height <= 0) {
document.getElementById('result').innerHTML = 'Please enter valid positive numbers for age, weight, and height.';
return;
}
// Convert weight to kg
var weightKg = (weightUnit === 'lbs') ? weight * 0.453592 : weight;
// Convert height to cm
var heightCm = (heightUnit === 'inches') ? height * 2.54 : height;
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;
}
var tdee = bmr * activityFactor;
var targetCalories = tdee;
// Adjust for goal
switch (goal) {
case 'mildLoss':
targetCalories -= 250; // 0.5 lbs/week
break;
case 'moderateLoss':
targetCalories -= 500; // 1 lbs/week
break;
case 'extremeLoss':
targetCalories -= 1000; // 2 lbs/week
break;
case 'mildGain':
targetCalories += 250; // 0.5 lbs/week
break;
case 'moderateGain':
targetCalories += 500; // 1 lbs/week
break;
case 'extremeGain':
targetCalories += 1000; // 2 lbs/week
break;
case 'maintain':
default:
// No change for maintain
break;
}
// Ensure target calories don't go too low
if (targetCalories < 1000) { // A very low arbitrary minimum for safety
targetCalories = 1000;
}
// Macronutrient Calculation
// Protein: ~1g per lb of body weight (convert weightKg back to lbs for this common recommendation)
var currentWeightLbs = (weightUnit === 'lbs') ? weight : weightKg * 2.20462;
var proteinGrams = currentWeightLbs * 1.0; // 1 gram per lb of body weight
var proteinCalories = proteinGrams * 4;
// Fat: ~25% of total calories
var fatCalories = targetCalories * 0.25;
var fatGrams = fatCalories / 9;
// Carbohydrates: Remaining calories
var carbCalories = targetCalories – proteinCalories – fatCalories;
var carbGrams = carbCalories / 4;
// Handle edge case where protein + fat might exceed target calories (e.g., very low-calorie diet)
if (carbCalories < 0) {
carbCalories = 0;
carbGrams = 0;
// Re-distribute remaining calories to fat if carbs are negative
fatCalories = targetCalories – proteinCalories;
fatGrams = fatCalories / 9;
if (fatCalories < 0) { // If even fat goes negative, cap fat and protein
fatCalories = 0;
fatGrams = 0;
proteinCalories = targetCalories;
proteinGrams = targetCalories / 4;
}
}
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