BMR Calculator
Your basal metabolic rate — the calories your body burns doing nothing at all. Every other number starts here.
Every formula, side by side
| Formula | BMR | Notes |
|---|
What you burn once you move
| Activity level | Daily burn |
|---|
Mifflin-St Jeor is the most reliable equation for most people and is what the headline number uses. Katch-McArdle is more accurate if you know your body fat percentage, because it works from lean mass rather than total weight, and it is shown whenever you enter one. Harris-Benedict is the original from 1919 and runs slightly high. Any of them is an estimate within roughly ten percent. General fitness information, not medical advice.
What your BMR actually tells you
Basal metabolic rate is what your body would burn if you lay still in a dark room for twenty four hours and did nothing — the cost of keeping your heart beating, your brain running and your tissue alive. For most adults it is somewhere between sixty and seventy percent of everything they burn in a day. It is the foundation every calorie target is built on, and it is the number people most often get wrong about themselves.
Which formula to trust
Mifflin-St Jeor is the one to use if all you know is your height, weight, age and sex. It has been tested against indirect calorimetry more than any other and it holds up. Katch-McArdle is better if you have a reliable body fat percentage, because it calculates from lean mass — and lean mass, not total weight, is what burns the calories. That is why two people at the same body weight can have BMRs two hundred calories apart. Harris-Benedict is included for comparison; it dates to 1919 and tends to overestimate.
Never eat at your BMR
This is the single most common mistake. People find their BMR, see a number like 1,800, and set that as their daily intake. That is a starvation diet with extra steps. You do not spend your day lying still. Multiply BMR by an activity factor to get what you actually burn, then take your deficit from that number. The table above does it for you.
Why it falls as you age, and what to do
BMR drops roughly one to two percent per decade after thirty, and almost all of that drop is lost muscle rather than some mysterious metabolic decline. Muscle is metabolically expensive tissue. Keep it, and most of the decline never happens. That is the entire argument for lifting heavy into your forties, fifties and beyond — not vanity, but the fact that it keeps your engine size.
Common questions
Is my metabolism broken? Almost certainly not. Measured BMR falls within about ten percent of predicted for the overwhelming majority of people. What is usually broken is the accuracy of the food logging.
Does eating more often raise BMR? No. The thermic cost of digesting food scales with how much you eat, not how many times you sit down.
Can I raise my BMR? Yes, by adding lean mass. It is slow and it is the only lever that genuinely works.
Next: Find your real daily burn → | Get your body fat percentage → | All calculators
