BMR Calculator (Basal Metabolic Rate)
Your BMR is the number of calories your body burns doing absolutely nothing — just breathing, circulating blood and staying alive. It's the foundation every calorie target is built on. This calculator uses the Mifflin-St Jeor equation, the most validated formula available.
How to use this calculator
- Enter your sex, age, height and weight.
- Press Calculate to see your BMR — the calories you'd burn lying still all day.
- Multiply by an activity factor (or use our calorie calculator) to get your real daily needs.
- Never set a calorie target below your BMR without medical supervision.
Formula used
Mifflin-St Jeor equation with W = weight (kg), H = height (cm), A = age (years). It estimates resting energy expenditure within 10% of measured values for most people — more accurate than the older Harris-Benedict formula.
Example calculation
A 30-year-old woman, 165 cm, 60 kg:
BMR = 10(60) + 6.25(165) − 5(30) − 161 = 600 + 1,031 − 150 − 161 = 1,320 kcal/day. Even fully sedentary, her real daily burn is about 1,320 × 1.2 ≈ 1,584 kcal.
What is basal metabolic rate?
BMR is the energy cost of being alive: powering your brain, heart, lungs, liver and cell repair while at complete rest. For most people it represents 60–70% of everything they burn in a day — more than exercise and daily movement combined.
Muscle tissue burns more at rest than fat, which is why strength training raises BMR over time and why BMR gently declines with age as muscle is lost. Sex, size and genetics set the baseline; crash dieting can temporarily suppress it, which is one reason extreme diets backfire.
Why use this calculator?
- Understand your metabolic baseline — the floor below which calorie targets become unsafe.
- See why two people the same weight can have very different calorie needs.
- Build any diet plan from an evidence-based number instead of an app's black box.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is calories burned at complete rest; TDEE (total daily energy expenditure) is BMR plus everything else — walking, working, exercising and digesting food. TDEE = BMR × activity factor, and it's the number you eat against.
Is it bad to eat below my BMR?
Occasionally dipping below BMR isn't dangerous, but sustained intake well below BMR risks muscle loss, nutrient deficiencies and metabolic adaptation. Effective fat-loss deficits come out of your TDEE, not your BMR.
How can I increase my BMR?
Build muscle — it's the most controllable factor. Strength training plus adequate protein raises resting burn over months. Sleep and not chronically under-eating also protect your metabolic rate.
Why is my BMR lower than my friend's?
BMR scales mainly with body size and muscle mass, then sex and age. A larger or more muscular person burns more at rest. Genetics adds roughly ±10% variation around the formula's estimate.