Understand Your Macros

This calculator uses the Mifflin-St Jeor equation, the gold standard recommended by the American Dietetic Association. It calculates your Basal Metabolic Rate (BMR) — the calories your body burns at complete rest:

Male: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age) + 5

Female: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age) – 161

Your BMR is then multiplied by an activity factor (1.2 to 1.9) to get your Total Daily Energy Expenditure (TDEE). Finally, calories are adjusted based on your goal, and macronutrients are split based on evidence-based ratios: 40/40/20 (protein/carbs/fat) for weight loss, and 30/40/30 for maintenance and muscle gain.

The Mifflin-St Jeor equation predicts resting metabolic rate within 10% of measured values for most people — both non-obese and obese — making it the most reliable formula available. However, individual metabolism varies based on genetics, muscle mass, hormones, and other factors. Use these numbers as a starting point and adjust based on your real-world results over 2-4 weeks.

Research consistently shows that 1.6 to 2.2 grams of protein per kilogram of body weight per day is optimal for muscle building. Going above 2.2 g/kg provides diminishing returns for most people. The macro splits in this calculator are designed to fall within this range for most users at their calculated calorie level.

The activity multiplier is the single biggest source of error in calorie calculations. Research shows people overestimate their activity level by an average of 51%. Be honest with your selection — if you exercise 3 times a week but sit at a desk the rest of the time, “Light” or “Moderate” is more accurate than “Active.” Overestimating means eating more than you need, which stalls fat loss.

Calories determine whether you gain or lose weight, but macros determine what you gain or lose. Without enough protein, you’ll lose muscle along with fat. Without enough fat, hormone production suffers. Tracking macros ensures you’re fueling your body optimally for your goal — not just hitting a calorie number. Even rough tracking (hitting within 10-15g of each target) produces significantly better results than calorie counting alone.

Yes, but it’s slower than focusing on one goal at a time. This is called “body recomposition” and works best for beginners, people returning to training after a break, and those with higher body fat. Select “Mild weight loss” and prioritize hitting your protein target — this preserves muscle while losing fat. A structured training program with progressive overload is essential for recomposition.