Calculate your daily protein, carbohydrate, and fat intake based on your body weight and activity level.
Sedentary (Little to no exercise)
Lightly Active (Exercise 1-3 days/week)
Moderately Active (Exercise 3-5 days/week)
Very Active (Exercise 6-7 days/week)
Extremely Active (Intense exercise daily, physical job)
Maintain Weight
Lose Fat (Caloric Deficit)
Gain Muscle (Caloric Surplus)
Understanding the Katy Hearn Macro Calculator
The Katy Hearn Macro Calculator is a tool designed to help individuals determine their daily macronutrient targets (protein, carbohydrates, and fats) based on their body weight, activity level, and fitness goals. This approach is central to many fitness and nutrition plans, including those popularized by fitness influencers like Katy Hearn, who advocate for structured eating to achieve specific physique results.
The Science Behind Macronutrients
Macronutrients are the nutrients your body needs in large amounts to provide energy and support various bodily functions. They consist of:
Protein: Essential for building and repairing tissues, muscle growth, enzyme production, and immune function.
Carbohydrates: The body's primary source of energy, crucial for fueling workouts and daily activities.
Fats: Important for hormone production, nutrient absorption, insulation, and providing a secondary energy source.
How the Calculator Works
This calculator utilizes a common methodology for estimating daily caloric and macronutrient needs. The process generally involves these steps:
Basal Metabolic Rate (BMR) Estimation: While this simplified calculator doesn't explicitly calculate BMR, it uses body weight as a primary factor, which is a key component in BMR calculations. BMR is the number of calories your body burns at rest.
Total Daily Energy Expenditure (TDEE) Calculation: Your TDEE is your BMR multiplied by an activity factor. The activity factor accounts for the calories burned through exercise and daily movement. Our calculator uses a selection of standard activity multipliers.
TDEE = Body Weight (kg) * Activity Factor * Constant (approx. 22 for general estimation)
*Note: The 'Constant' (approx. 22) is a simplification. More precise formulas like Mifflin-St Jeor or Harris-Benedict are often used for BMR, which then gets multiplied by the activity factor to get TDEE. This calculator uses a direct TDEE estimation from weight and activity factor for simplicity.*
Lose Fat (Cut): Caloric intake is set at a deficit (e.g., TDEE – 500 calories).
Gain Muscle (Bulk): Caloric intake is set at a surplus (e.g., TDEE + 300-500 calories).
Macronutrient Distribution: Based on the target calories and the chosen goal, the macros are typically distributed as follows (this is a common framework, and personal ratios may vary):
Protein: Often set high, around 1.6 to 2.2 grams per kilogram of body weight. (e.g., Body Weight (kg) * 2g/kg)
Fats: Typically set to a moderate percentage of total calories, often around 20-30%. (e.g., Total Daily Calories * 0.25 / 9 kcal/g)
Carbohydrates: The remaining calories are filled with carbohydrates. (e.g., (Total Daily Calories – (Protein Grams * 4) – (Fat Grams * 9)) / 4 kcal/g)
*Note: Protein and fat targets are calculated first, and carbohydrates fill the remainder.*
Using the Calculator Effectively
Enter your current body weight in kilograms, select your typical weekly activity level, and choose your primary fitness goal. The calculator will provide estimated daily targets for protein, carbohydrates, and fats.
Remember that these are estimates. Individual metabolic rates, body composition, and responses to diet can vary. It's advisable to use these numbers as a starting point and adjust them based on your progress, how you feel, and professional guidance if necessary. Consistency and adherence to your plan are key to achieving your fitness objectives.
function calculateMacros() {
var weightKg = parseFloat(document.getElementById("weightKg").value);
var activityLevel = parseFloat(document.getElementById("activityLevel").value);
var goal = document.getElementById("goal").value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(weightKg) || weightKg <= 0) {
resultDiv.innerHTML = "Please enter a valid body weight in kilograms.";
return;
}
// Simplified TDEE Calculation: Weight (kg) * Activity Factor * 22 (general multiplier)
// This is a common simplification; more complex BMR formulas exist.
var estimatedTdee = weightKg * activityLevel * 22;
var targetCalories;
if (goal === "cut") {
targetCalories = estimatedTdee – 500; // Caloric deficit for fat loss
} else if (goal === "bulk") {
targetCalories = estimatedTdee + 300; // Caloric surplus for muscle gain
} else { // maintain
targetCalories = estimatedTdee; // Maintain current weight
}
// Ensure target calories are not unrealistically low
if (targetCalories < 1200) {
targetCalories = 1200;
}
// Macronutrient Calculations (using common ratios)
// Protein: ~2g per kg of body weight (a common starting point for active individuals)
var proteinGrams = weightKg * 2;
var proteinCalories = proteinGrams * 4; // 4 calories per gram of protein
// Fats: ~25% of total target calories (a common moderate fat intake)
var fatCalories = targetCalories * 0.25;
var fatGrams = fatCalories / 9; // 9 calories per gram of fat
// Carbohydrates: Remaining calories
var carbCalories = targetCalories – proteinCalories – fatCalories;
var carbGrams = carbCalories / 4; // 4 calories per gram of carbohydrate
// Ensure carb grams are not negative due to extreme deficits/surpluses or rounding
if (carbGrams < 0) {
carbGrams = 0; // Cannot have negative carbs
// Re-adjust calories if carbs are forced to 0, though this is rare with typical goals
// For simplicity here, we'll just display 0 carbs if it becomes negative.
}
resultDiv.innerHTML =
"Your Daily Targets:" +
targetCalories.toFixed(0) + " Calories" +
"" +
"Protein: " + proteinGrams.toFixed(0) + "g | " +
"Carbohydrates: " + carbGrams.toFixed(0) + "g | " +
"Fats: " + fatGrams.toFixed(0) + "g" +
"";
}