TDEE & Macro Calculator
BMR / TDEE from Mifflin-St Jeor plus a configurable macro split.
Overview
A TDEE and macro calculator turns four inputs — age, sex, weight, height — and an activity level into a daily calorie target, then splits that target into grams of protein, carbohydrate, and fat. It is the foundation of most evidence-based body-composition coaching, because tracking macros (rather than just total calories) accounts for the fact that 100 grams of protein and 100 grams of fat behave very differently in the body.
The output is a planning baseline. Real metabolism varies by 10–15% even between identical-looking individuals, and adaptive thermogenesis means the number drifts as your weight changes. Treat the figures as a starting point, adjust based on two to four weeks of weight-trend data, and let the scale and tape measure tell you whether the target is right.
How it works
Basal metabolic rate (BMR) is computed with the Mifflin-St Jeor equation, which is more accurate than the older Harris-Benedict formula:
- Men:
BMR = 10 × kg + 6.25 × cm − 5 × age + 5 - Women:
BMR = 10 × kg + 6.25 × cm − 5 × age − 161
Total daily energy expenditure (TDEE) is BMR multiplied by an activity factor — typically 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (very active), 1.9 (athlete). The calculator then applies a configurable surplus or deficit (commonly ±15–25% for cutting or bulking) and splits the resulting kcal target into macros. Standard kcal-per-gram conversions are 4 for protein, 4 for carbs, and 9 for fat. A typical 40/30/30 split for 2,000 kcal yields 200 g carbs, 150 g protein, and 67 g fat.
Examples
- Man, 30 years, 80 kg, 180 cm, moderate activity: BMR = 800 + 1125 − 150 + 5 = 1780 kcal; TDEE = 1780 × 1.55 ≈ 2760 kcal.
- Woman, 28 years, 60 kg, 165 cm, light activity: BMR = 600 + 1031 − 140 − 161 = 1330 kcal; TDEE ≈ 1830 kcal.
- 2,500 kcal cut at 40/30/30: 250 g carbs, 188 g protein, 83 g fat.
- 3,000 kcal lean-bulk at 50/25/25: 375 g carbs, 188 g protein, 83 g fat.
FAQ
Why Mifflin-St Jeor over Harris-Benedict?
It was fit to a more recent and broader population and on average errs by about 100 kcal less per day than the older equation.
How accurate is the activity multiplier?
It is the noisiest part of the model. Two people who both "exercise three times a week" may differ by 500 kcal per day in real burn.
Do I need exactly 1 g of protein per pound?
Roughly 1.6–2.2 g per kilogram supports muscle retention in a deficit. More than that yields diminishing returns.
Why does my weight stall even at the calculated deficit?
Adaptive thermogenesis, water shifts, and food-logging error commonly explain stalls. Re-measure trend weight over two to three weeks before adjusting.