Phase 6 · Biometric & Longevity

Basal Metabolic Rate & Calorie Calculator

Your maintenance calories aren't a guess from a chart — they're a formula. Solve your BMR and TDEE with two clinical equations, body-fat-aware, and get your real targets.

Educational estimate, not medical advice. These equations approximate energy needs for healthy adults and can't account for medical conditions, medications or individual variation. Consult a doctor or registered dietitian before changing your diet, especially if you have a health condition.

How do you calculate your BMR and daily calories?

BMR is the energy you burn at complete rest. The Mifflin-St Jeor equation gives it as 10×weight(kg) + 6.25×height(cm) − 5×age, then +5 for men or −161 for women. If you know your body-fat percentage, Katch-McArdle uses lean mass instead: 370 + 21.6×lean kg. Daily calories (TDEE) = BMR × your activity factor.

Common activity factors: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 active, 1.9 athlete.
Lean body mass = weight × (1 − body fat %). Katch-McArdle is usually more precise for very lean or very muscular people, where weight-based formulas drift.
A deficit of about 500 kcal/day below TDEE is roughly 1 lb of fat loss per week, since ~3,500 kcal ≈ 1 lb of fat.
Mifflin-St Jeor was published in Am J Clin Nutr (1990) and is the most validated general equation. These are population estimates, not medical advice.

Under the hood

The formulas, fully cited

Two peer-reviewed equations, computed live (weight converted to kg, height to cm):

Mifflin-St Jeor = 10·kg + 6.25·cm − 5·age + s (s = +5 male, −161 female)

Lean body mass = weight × (1 − body fat %)

Katch-McArdle = 370 + 21.6 × lean body mass (kg)

TDEE = BMR × activity factor

Fat-loss target = TDEE − 500 kcal (≈ 1 lb/week)

Source — Mifflin-St Jeor: Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241–247.
Source — Katch-McArdle: Katch & McArdle, lean-mass formula from Exercise Physiology: Energy, Nutrition, and Human Performance.
Why body fat matters: muscle burns more at rest than fat, so two people of the same weight can have different BMRs. The lean-mass equation captures that; the weight-based one can't.

Your directives

What to do next, based on your numbers

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Answers

Frequently asked questions

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the energy your body burns at complete rest just to stay alive — breathing, circulation, cell repair. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor to account for movement, exercise and digestion. TDEE is the number that matters for eating to maintain, lose or gain weight.

Mifflin-St Jeor vs Katch-McArdle — which is more accurate?

Mifflin-St Jeor uses height, weight, age and sex and is the most validated general equation. Katch-McArdle uses your lean body mass instead, so when you know your body-fat percentage with reasonable accuracy, it is usually more precise — especially for very lean or very muscular people, where weight-based formulas drift. This tool shows both and leads with Katch-McArdle when body fat is provided.

How many calories should I eat to lose weight?

A deficit of about 500 calories per day below your TDEE produces roughly 1 pound of fat loss per week (since ~3,500 calories ≈ 1 lb). Larger deficits lose faster but are harder to sustain and risk muscle loss. As a rule of thumb, avoid eating below your BMR for long stretches.

How much protein should I eat?

For preserving muscle in a deficit or building it in a surplus, a common evidence-based target is roughly 0.7–1.0 gram of protein per pound of lean body mass (or of goal body weight). This calculator estimates a target from your lean mass; adjust to your goals and any medical guidance.

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