BMR calculator
What your body spends before you move a muscle — and, just as usefully, what that number does not mean.
How this is calculated
The Mifflin–St Jeor equation, published in 1990 and still the default in clinical practice:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s
s = +5 for men, −161 for women Notice what it does not ask for: body composition, hormones, sleep, temperature. It is a population average fitted to height, weight, age and sex, and it lands within about ±10 % for most people — wider at the extremes. That is accurate enough to plan from and not accurate enough to argue with the scale about.
Why you should not eat your BMR
It is the cost of being alive and motionless. Walking to the kitchen is not in it. Eating at that number means a deficit far larger than intended, which is where lost muscle and abandoned diets come from. Multiply by an activity factor first — that is what the calorie calculator does.
These are the same numbers and the same guards the Talk2Fit app applies when it builds your plan — the calculator is the app's own arithmetic, not a separate approximation.
Questions
What is BMR, exactly?
The energy your body spends doing nothing: breathing, circulating blood, keeping your brain and organs running. Measured at rest, awake, fasted, in a neutral room. It is typically 60–70 % of everything you burn in a day.
Is BMR the same as what I should eat?
No, and eating at your BMR is a common and costly mistake. It excludes movement, digestion and exercise. Multiply it by an activity factor to get total daily burn — that is the number a diet is built on.
Why Mifflin–St Jeor and not Harris–Benedict?
Harris–Benedict came from 1919 data and overestimates for modern body compositions. Mifflin–St Jeor was validated in 1990 against a broader population and is the equation most dietetic practice defaults to today.
Does muscle change the answer?
Yes, and this equation cannot see it — it only knows height, weight, age and sex. Two people at the same weight, one lean and one not, have measurably different resting rates. If you know your body-fat percentage, Katch–McArdle is the better fit; for everyone else the difference is smaller than day-to-day noise.