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Macronutrient Calculator

Calculate your daily split of protein, carbs, and fats based on your goal (maintenance, weight loss, or muscle gain). Mifflin-St Jeor + ISSN guidelines.

Sources: Mifflin-St Jeor et al. (1990) — Predictive equation for resting energy expenditure · ISSN Position Stand — Diets and Body Composition

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How to Calculate Daily Macronutrients

Knowing the right split of protein, carbohydrates, and fats is fundamental for reaching any nutritional goal, whether it is weight loss, maintenance, or muscle gain. Macro calculation starts from individual caloric needs and divides them according to optimal percentages for your goal.

The Calculation Formula

This calculator uses the Mifflin-St Jeor formula to determine Basal Metabolic Rate (BMR):

  • Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5
  • Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161

BMR is multiplied by the activity factor to get TDEE (Total Daily Energy Expenditure). Based on your selected goal, calories are adjusted:

  • Maintenance: calories = TDEE (30% protein, 40% carbs, 30% fats)
  • Weight loss: calories = TDEE - 500 kcal (35% protein, 35% carbs, 30% fats)
  • Muscle gain: calories = TDEE + 300 kcal (30% protein, 45% carbs, 25% fats)

Why Percentages Change Based on Goal

During weight loss, protein is increased to 35% to preserve muscle mass during the caloric deficit, as recommended by the ISSN. During muscle gain, carbohydrates rise to 45% to provide sufficient energy for intense training and support muscle protein synthesis.

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Frequently Asked Questions

What are macronutrients?▼
Macronutrients are the three main nutrients that provide energy: protein, carbohydrates, and fats. Protein provides 4 kcal per gram and is essential for muscle building and maintenance. Carbohydrates provide 4 kcal per gram and are the main energy source. Fats provide 9 kcal per gram and are fundamental for hormonal functions and fat-soluble vitamin absorption.
What is the ideal macro split?▼
There is no universal split: it depends on the goal. For weight maintenance, general guidelines suggest 45-60% carbs, 10-35% protein, and 20-35% fats. For weight loss, increase protein (30-35%) to preserve muscle mass. For muscle gain, prioritize carbs (40-50%) to support intense training.
How do you calculate calories from each macronutrient?▼
Each macronutrient has a specific energy value: protein and carbs provide 4 kcal per gram, fats 9 kcal per gram. If your requirement is 2000 kcal and 30% should come from protein: 2000 x 0.30 = 600 kcal from protein, divided by 4 = 150 g of protein per day.