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 or 2x training)
0.25 kg (slow & sustainable)
0.5 kg (recommended)
0.75 kg (faster)
1 kg (very fast, requires significant deficit)
Understanding Macro Calculation for Weight Loss
Calculating your macronutrient (macros) targets is a fundamental step in a structured weight loss journey. Macros refer to the three main food components your body needs in large amounts: carbohydrates, proteins, and fats. By understanding your caloric needs and the roles of each macro, you can create a diet that supports fat loss while preserving muscle mass and maintaining energy levels.
The process involves several steps: determining your Basal Metabolic Rate (BMR), calculating your Total Daily Energy Expenditure (TDEE), applying a calorie deficit for weight loss, and finally distributing those calories among protein, carbohydrates, and fats.
1. Basal Metabolic Rate (BMR)
Your BMR is the number of calories your body burns at rest to maintain basic life functions. We use the Mifflin-St Jeor equation, which is considered one of the most accurate:
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
2. Total Daily Energy Expenditure (TDEE)
Your TDEE is the total number of calories you burn in a day, including your BMR and calories burned through physical activity and digestion. It's 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
3. Calorie Deficit for Weight Loss
To lose weight, you need to consume fewer calories than your TDEE. A safe and sustainable rate of weight loss is typically 0.5 kg (approximately 1 lb) per week, which requires a deficit of about 500 calories per day (3500 calories = 1 lb of fat). The calculator adjusts your TDEE based on your chosen weekly weight loss goal:
1 kg deficit per week ≈ 1000 calorie deficit per day
0.75 kg deficit per week ≈ 750 calorie deficit per day
0.5 kg deficit per week ≈ 500 calorie deficit per day
0.25 kg deficit per week ≈ 250 calorie deficit per day
The target daily calorie intake is then: Target Calories = TDEE - (Weekly Goal * 7700 / 7) (approximately 1100 calories per kg of fat).
4. Macronutrient Distribution
Once you have your target daily calories, you need to distribute them among protein, carbohydrates, and fats. A common approach for weight loss that helps preserve muscle mass is:
Protein: Aim for 1.6-2.2 grams per kg of body weight. Protein is satiating and helps maintain muscle during a deficit. (4 calories per gram)
Fats: Aim for 20-30% of your total daily calories. Healthy fats are crucial for hormone production and overall health. (9 calories per gram)
Carbohydrates: Fill the remaining calories with carbohydrates. Carbs provide energy for workouts and daily activities. (4 calories per gram)
The calculator will first determine your protein and fat needs and then allocate the remaining calories to carbohydrates.
Example Calculation
Let's consider a 30-year-old male, weighing 80 kg, standing 180 cm tall, who is moderately active and wants to lose 0.5 kg per week.
Protein: Let's aim for 1.8g/kg. 80 kg * 1.8g/kg = 144g of protein. (144g * 4 cal/g = 576 calories from protein).
Fats: Let's aim for 25% of calories. 2259 * 0.25 = 565 calories from fat. (565 cal / 9 cal/g ≈ 63g of fat).
Carbohydrates: Remaining calories. 2259 (total) – 576 (protein) – 565 (fat) = 1118 calories from carbs. (1118 cal / 4 cal/g ≈ 280g of carbohydrates).
So, the target macros for this individual would be approximately 144g Protein, 280g Carbohydrates, and 63g Fat, totaling around 2259 calories per day.
Remember, these are estimates. Adjust based on your body's response, energy levels, and adherence. Consulting with a healthcare professional or registered dietitian is always recommended for personalized advice.
function calculateMacros() {
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 weightLossGoal = parseFloat(document.getElementById("weightLossGoal").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
if (isNaN(weight) || isNaN(height) || isNaN(age) || weight <= 0 || height <= 0 || age <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for weight, height, and age.";
return;
}
// Calculate BMR using Mifflin-St Jeor equation
var bmr;
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// Calculate TDEE based on activity level
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 tdee = bmr * activityMultiplier;
// Calculate calorie deficit for weight loss
// Approx 7700 calories per kg of fat
var caloriesPerKgFat = 7700;
var dailyDeficit = weightLossGoal * (caloriesPerKgFat / 7);
var targetCalories = tdee – dailyDeficit;
// Ensure target calories are not excessively low
if (targetCalories < 1200) {
targetCalories = 1200; // Minimum safe intake for women, slightly higher for men
if (gender === "male" && targetCalories < 1500) {
targetCalories = 1500;
}
}
// Calculate Macros
// Protein: 1.6-2.2 g/kg body weight
var proteinGrams = weight * 1.8; // Using a mid-range value
var proteinCalories = proteinGrams * 4;
// Fats: 20-30% of total calories
var fatPercentage = 0.25; // Using a mid-range value
var fatCalories = targetCalories * fatPercentage;
var fatGrams = fatCalories / 9;
// Carbohydrates: Remaining calories
var carbCalories = targetCalories – proteinCalories – fatCalories;
var carbGrams = carbCalories / 4;
// Round to nearest whole number or one decimal place for precision
proteinGrams = Math.round(proteinGrams);
fatGrams = Math.round(fatGrams);
carbGrams = Math.round(carbGrams);
targetCalories = Math.round(targetCalories);
resultDiv.innerHTML =
"Estimated Daily Calories: " + targetCalories + " kcal" +
"Protein: " + proteinGrams + " g" +
"Carbohydrates: " + carbGrams + " g" +
"Fats: " + fatGrams + " g";
}