Use this calculator to estimate your daily calorie needs and recommended macronutrient breakdown (protein, carbohydrates, and fats) based on your personal data and fitness goals.
Male
Female
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/week)
Extra Active (very hard exercise/physical job/training twice a day)
Maintain Weight
Mild Weight Loss (0.25 kg/week)
Moderate Weight Loss (0.5 kg/week)
Extreme Weight Loss (0.75 kg/week)
Mild Weight Gain (0.25 kg/week)
Moderate Weight Gain (0.5 kg/week)
Extreme Weight Gain (0.75 kg/week)
function calculateMacros() {
var age = parseFloat(document.getElementById("age").value);
var gender = document.getElementById("gender").value;
var weight = parseFloat(document.getElementById("weight").value); // kg
var height = parseFloat(document.getElementById("height").value); // cm
var activityLevel = 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("macroResult").innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Step 1: Calculate Basal Metabolic Rate (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;
}
// Step 2: Calculate Total Daily Energy Expenditure (TDEE)
var activityFactor;
switch (activityLevel) {
case "sedentary":
activityFactor = 1.2;
break;
case "light":
activityFactor = 1.375;
break;
case "moderate":
activityFactor = 1.55;
break;
case "very":
activityFactor = 1.725;
break;
case "extra":
activityFactor = 1.9;
break;
default:
activityFactor = 1.2; // Default to sedentary
}
var tdee = bmr * activityFactor;
// Step 3: Adjust TDEE for Goal
var dailyCalories;
var calorieAdjustment;
switch (goal) {
case "maintain":
calorieAdjustment = 0;
break;
case "mildLoss":
calorieAdjustment = -250; // Approx 0.25 kg/week loss
break;
case "moderateLoss":
calorieAdjustment = -500; // Approx 0.5 kg/week loss
break;
case "extremeLoss":
calorieAdjustment = -750; // Approx 0.75 kg/week loss
break;
case "mildGain":
calorieAdjustment = 250; // Approx 0.25 kg/week gain
break;
case "moderateGain":
calorieAdjustment = 500; // Approx 0.5 kg/week gain
break;
case "extremeGain":
calorieAdjustment = 750; // Approx 0.75 kg/week gain
break;
default:
calorieAdjustment = 0;
}
dailyCalories = tdee + calorieAdjustment;
// Ensure daily calories don't go too low (e.g., below BMR for extreme loss)
if (dailyCalories < bmr * 0.8) { // Arbitrary lower limit to prevent dangerously low intake
dailyCalories = bmr * 0.8;
document.getElementById("macroResult").innerHTML += "Warning: Calculated calories were adjusted upwards to ensure a minimum healthy intake.";
}
if (dailyCalories < 1200 && gender === "female") {
dailyCalories = 1200;
document.getElementById("macroResult").innerHTML += "Warning: Calculated calories for women were adjusted upwards to a minimum of 1200 kcal/day for health reasons.";
}
if (dailyCalories < 1500 && gender === "male") {
dailyCalories = 1500;
document.getElementById("macroResult").innerHTML += "Warning: Calculated calories for men were adjusted upwards to a minimum of 1500 kcal/day for health reasons.";
}
// Step 4: Calculate Macronutrient Distribution
// Common recommendations:
// Protein: 1.6 – 2.2g per kg of body weight for active individuals. Let's use 1.8g/kg as a default.
// Fats: 20-35% of total calories. Let's use 25%.
// Carbs: Remaining calories.
var proteinGrams = weight * 1.8; // 1.8g per kg body weight
var proteinCalories = proteinGrams * 4; // 4 kcal/gram
var fatCalories = dailyCalories * 0.25; // 25% of total calories from fat
var fatGrams = fatCalories / 9; // 9 kcal/gram
var carbCalories = dailyCalories – proteinCalories – fatCalories;
var carbGrams = carbCalories / 4; // 4 kcal/gram
// Ensure no negative carb calories due to very low calorie goals or high protein/fat targets
if (carbCalories < 0) {
carbCalories = 0;
carbGrams = 0;
// Redistribute the "missing" carb calories to protein/fat if necessary, or just cap carbs at 0
// For simplicity, we'll just cap carbs at 0 and acknowledge the protein/fat targets might be too high for the calorie goal.
document.getElementById("macroResult").innerHTML += "Warning: Carbohydrate intake was set to 0 as the calorie goal is very low relative to protein and fat targets. Consider adjusting your goal or macro percentages.";
}
// Display results
var resultHTML = "
A macronutrient diet, often simply called "counting macros," involves tracking the amount of protein, carbohydrates, and fats you consume daily. These three macronutrients are essential for energy, growth, and repair, and their balance plays a crucial role in achieving various health and fitness goals, from weight loss and muscle gain to improved athletic performance.
What are Macronutrients?
Protein: Often called the building block of the body, protein is vital for muscle repair and growth, enzyme production, hormone regulation, and immune function. It provides 4 calories per gram. Good sources include lean meats, poultry, fish, eggs, dairy, legumes, and tofu.
Carbohydrates: The body's primary source of energy, carbohydrates fuel your brain, muscles, and organs. They also provide 4 calories per gram. They are found in grains, fruits, vegetables, and legumes. Complex carbohydrates (whole grains, vegetables) offer sustained energy and fiber, while simple carbohydrates (sugars) provide quick energy.
Fats: Essential for hormone production, nutrient absorption (especially fat-soluble vitamins A, D, E, K), and protecting organs. Fats are the most calorie-dense macronutrient, providing 9 calories per gram. Healthy fats come from avocados, nuts, seeds, olive oil, and fatty fish.
Why Count Macros?
While calorie counting focuses solely on energy intake, macro counting provides a more nuanced approach by considering the source of those calories. This allows for:
Targeted Goals: Whether you aim for weight loss, muscle gain, or maintenance, specific macro ratios can optimize your results. For instance, higher protein intake is often recommended for muscle building and satiety during weight loss.
Improved Body Composition: By ensuring adequate protein, you can preserve muscle mass during a calorie deficit, leading to a better body composition.
Better Energy Levels: Balancing carbs and fats can help stabilize blood sugar and provide consistent energy throughout the day.
Dietary Flexibility: Unlike restrictive diets, macro counting allows for a wider variety of foods, as long as they fit your daily targets.
How the Calculator Works
Our Macronutrient Diet Calculator uses scientifically recognized formulas to estimate your daily needs:
Basal Metabolic Rate (BMR): This is the number of calories your body burns at rest to maintain basic bodily functions (breathing, circulation, cell production). We use the Mifflin-St Jeor equation, which is widely considered one of the most accurate BMR formulas.
Total Daily Energy Expenditure (TDEE): Your BMR is then multiplied by an activity factor to account for the calories you burn through daily activities and exercise.
Goal Adjustment: Based on your selected goal (weight loss, gain, or maintenance), a calorie deficit or surplus is applied to your TDEE to help you achieve your objective. For example, a 500 kcal deficit typically leads to about 0.5 kg (1 lb) of weight loss per week.
Macronutrient Distribution: Finally, your total daily calories are broken down into protein, carbohydrates, and fats. Our calculator uses a common approach:
Protein: Calculated at approximately 1.8 grams per kilogram of your body weight, which is suitable for active individuals aiming for muscle maintenance or growth.
Fats: Set at 25% of your total daily calories, providing essential fatty acids and supporting hormone function.
Carbohydrates: The remaining calories are allocated to carbohydrates, providing the necessary energy for your activities.
Using Your Results
Once you have your estimated macronutrient targets, you can use a food tracking app or journal to log your food intake and ensure you're hitting your daily goals. Remember that these are starting points, and you may need to adjust your macros based on how your body responds, your energy levels, and your progress towards your goals.
Important Disclaimer: This calculator provides estimates based on general guidelines. Individual nutritional needs can vary significantly due to genetics, metabolism, specific health conditions, and training intensity. Always consult with a qualified healthcare professional or a registered dietitian before making significant changes to your diet or exercise routine, especially if you have underlying health concerns.