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)
Macronutrients are the nutrients your body needs in large amounts to provide energy and support overall bodily functions. The three primary macronutrients are protein, fat, and carbohydrates. Understanding how to calculate your ideal intake of each is crucial for achieving your health and fitness goals, whether it's weight loss, muscle gain, or simply maintaining a healthy lifestyle.
Basal Metabolic Rate (BMR)
The first step in determining your macronutrient needs is estimating your 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. We use the Mifflin-St Jeor equation, which is widely considered one of the most accurate formulas:
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
Total Daily Energy Expenditure (TDEE)
Your BMR represents your calorie needs at rest. However, your Total Daily Energy Expenditure (TDEE) accounts for your activity level. TDEE is calculated by multiplying your BMR by an activity factor:
Sedentary: BMR x 1.2
Lightly Active: BMR x 1.375
Moderately Active: BMR x 1.55
Very Active: BMR x 1.725
Extra Active: BMR x 1.9
This TDEE is your estimated daily calorie intake for maintaining your current weight.
Calorie Adjustments for Goals
To achieve specific goals, you need to adjust your TDEE:
Maintain Weight: Consume calories equal to your TDEE.
Gain Muscle Slowly (approx. 0.5 lb/week): Increase TDEE by 250 calories/day.
Gain Muscle Quickly (approx. 1 lb/week): Increase TDEE by 500 calories/day.
Note: Aggressive calorie deficits or surpluses can be unsustainable and may lead to muscle loss or excessive fat gain, respectively. Always listen to your body and consult a healthcare professional.
Macronutrient Ratios
Once you have your target daily calorie intake, you can determine your macronutrient distribution. While ratios can vary based on individual needs and preferences, here are common guidelines:
Protein: Essential for muscle repair and growth. Aim for 1.6-2.2 grams per kilogram of body weight for muscle gain/retention, or around 15-30% of total calories. (4 calories per gram)
Fat: Crucial for hormone production and nutrient absorption. Aim for 20-35% of total calories. (9 calories per gram)
Carbohydrates: The body's primary energy source. The remaining calories after protein and fat are allocated to carbohydrates. Aim for 45-65% of total calories. (4 calories per gram)
This calculator uses a common approach to set these targets based on your goals and activity.
Example Calculation:
Let's say a 30-year-old male, weighing 80kg, standing 180cm tall, who is moderately active, wants to maintain his weight.
This provides a solid starting point for understanding your daily macronutrient needs. Individual responses may vary, so monitoring progress and adjusting as needed is key.
function calculateMacros() {
var weightKg = parseFloat(document.getElementById("weightKg").value);
var heightCm = parseFloat(document.getElementById("heightCm").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 activityMultiplier;
switch (activityLevel) {
case "sedentary":
activityMultiplier = 1.2;
break;
case "lightly_active":
activityMultiplier = 1.375;
break;
case "moderately_active":
activityMultiplier = 1.55;
break;
case "very_active":
activityMultiplier = 1.725;
break;
case "extra_active":
activityMultiplier = 1.9;
break;
default:
activityMultiplier = 1.2; // Default to sedentary
}
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 * activityMultiplier;
var targetCalories;
switch (goal) {
case "lose_weight_slow":
targetCalories = tdee – 250;
break;
case "lose_weight_fast":
targetCalories = tdee – 500;
break;
case "maintain_weight":
targetCalories = tdee;
break;
case "gain_muscle_slow":
targetCalories = tdee + 250;
break;
case "gain_muscle_fast":
targetCalories = tdee + 500;
break;
default:
targetCalories = tdee; // Default to maintain
}
// Ensure target calories are not excessively low or high, and are positive
if (targetCalories 4000) targetCalories = 4000;
var proteinGrams;
var fatGrams;
var carbsGrams;
// Common macro split for balanced intake, adjusted slightly by goal
var proteinRatio, fatRatio, carbRatio;
if (goal.startsWith("lose_weight")) {
// Higher protein for satiety and muscle preservation during deficit
proteinRatio = 0.35; // 35%
fatRatio = 0.25; // 25%
carbRatio = 0.40; // 40%
} else if (goal.startsWith("gain_muscle")) {
// Higher protein and carbs for energy and growth
proteinRatio = 0.30; // 30%
fatRatio = 0.25; // 25%
carbsRatio = 0.45; // 45%
} else { // Maintain or no specific goal set
proteinRatio = 0.30; // 30%
fatRatio = 0.30; // 30%
carbRatio = 0.40; // 40%
}
// Ensure ratios add up to 100% if adjusted
var sumRatios = proteinRatio + fatRatio + carbRatio;
if (sumRatios !== 1) {
var scale = 1 / sumRatios;
proteinRatio *= scale;
fatRatio *= scale;
carbRatio *= scale;
}
proteinGrams = (targetCalories * proteinRatio) / 4;
fatGrams = (targetCalories * fatRatio) / 9;
carbsGrams = (targetCalories * carbRatio) / 4;
// Round to nearest whole number or one decimal place for readability
proteinGrams = Math.round(proteinGrams);
fatGrams = Math.round(fatGrams);
carbsGrams = Math.round(carbsGrams);
targetCalories = Math.round(targetCalories);
document.getElementById("caloriesResult").textContent = targetCalories.toLocaleString();
document.getElementById("proteinResult").textContent = proteinGrams.toLocaleString();
document.getElementById("fatResult").textContent = fatGrams.toLocaleString();
document.getElementById("carbsResult").textContent = carbsGrams.toLocaleString();
}