BMR Calculator

What is BMR and Why Does It Matter?

Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — the energy required to maintain basic life functions: breathing, circulation, cell production, temperature regulation, and organ function. BMR accounts for roughly 60–70% of total daily calorie expenditure for sedentary people.

Understanding your BMR is the foundation of any calorie-based diet or nutrition plan. It tells you the absolute minimum calories your body needs — eating below BMR for extended periods causes muscle loss and metabolic slowdown.

The Four BMR Formulas Compared

Formula	Accuracy	Best For
Mifflin-St Jeor (1990)	±10%, highest validated	General population
Harris-Benedict (1919, revised 1984)	±10–15%	General population, older formula
Katch-McArdle	±5–8% when BF% accurate	People who know body fat %
Cunningham	±5%	Athletes, lean individuals

Mifflin Male: 10w + 6.25h − 5a + 5 Mifflin Female: 10w + 6.25h − 5a − 161 Harris Male: 88.362 + 13.397w + 4.799h − 5.677a Katch-McArdle: 370 + 21.6 × Lean Mass(kg)

Frequently Asked Questions

The Mifflin-St Jeor equation is considered the most accurate for the general population based on multiple validation studies. The Katch-McArdle formula is more accurate for lean individuals when body fat percentage is known. Use Mifflin-St Jeor as your default.

Eating exactly at your BMR creates a deficit (since TDEE is higher) and will cause weight loss. However, very low-calorie diets (below BMR) cause rapid loss initially but trigger adaptive thermogenesis — your body lowers its BMR as a defense mechanism, making continued loss harder.

Yes. BMR decreases with age (roughly 1–2% per decade after 30), primarily due to loss of muscle mass. Resistance training counteracts this by preserving or increasing lean mass. BMR also temporarily decreases after prolonged calorie restriction — one reason diets become harder over time.

Muscle tissue burns about 3× more calories at rest than fat tissue. Each kilogram of muscle burns approximately 13 kcal/day at rest. Building muscle through resistance training gradually increases BMR, which is why strength training is recommended for sustainable long-term weight management.