BMR Calculator

Basal metabolic rate is the energy your body uses at complete rest over a day. This calculator uses the Mifflin-St Jeor equation, the current clinical default: for men, 10 × weight in kg + 6.25 × height in cm − 5 × age + 5; for women the final term is −161 instead. Choosing an activity level converts that into total daily energy expenditure.

How to use

1. Enter sex, height, weight and age.
2. Pick an activity level — roughly 1.2 for desk work with little exercise, 1.55 for training three to five times a week.
3. Read the basal rate and the activity-adjusted daily total.
4. For weight loss, subtract 300 to 500 kcal from the daily total to set an intake target.

When you actually need this

• Setting a daily calorie target at the start of a diet.
• Recalculating the target at a new bodyweight when progress stalls.
• Working out the surplus needed to gain weight deliberately.
• Updating the estimate after your training volume changes.

How accurate the equation is

Mifflin-St Jeor, published in 1990, has repeatedly validated closer to measured values than the older Harris-Benedict equation, which is why clinical nutrition generally starts there. Individual variation remains: two people matching on every input can differ by around ten percent, and at the extremes of body composition the Katch-McArdle equation, which works from lean mass, fits better. The larger error is usually the activity multiplier rather than the equation — the gap between 1.2 and 1.55 is several hundred calories a day, and most people overestimate their own activity. Tracking weight against intake for two or three weeks and working backwards gives a more reliable maintenance figure than any formula.

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FAQ

What formula does BMR Calculator use?

It uses the standard published formula for this calculation, applied exactly as written with no rounding until the final result. The inputs you provide are the only variables — there are no hidden assumptions or regional adjustments.

How accurate is the result from BMR Calculator?

The arithmetic is exact to the precision your browser supports. Accuracy in practice depends on your inputs: an estimate built on rounded figures will itself be an estimate, so enter the most precise values you have.

Can I use this for official or financial decisions?

Treat the output as a well-calculated estimate rather than professional advice. For medical, tax, legal or lending decisions, confirm the figure with a qualified professional or the institution involved before acting on it.