What BMR is
Your Basal Metabolic Rate is the energy your body spends at complete rest — the calories it takes just to breathe, circulate blood and keep your cells running. It’s the floor of your daily burn, before you move at all, and for most people it’s the biggest single slice of the calories they use in a day.
Why a range, not a number
The published equations disagree — Mifflin–St Jeor, the two Harris–Benedict versions, WHO/FAO and (with body fat) Katch–McArdle can land a hundred calories or more apart for the same person, because each was fitted on a different population. A single tidy figure hides that. We run five formulas and show the spread, so you read the uncertainty instead of trusting a false decimal.
BMR is at rest — add activity for TDEE
BMR is only the resting floor. Multiply it by how active you are and you get your TDEE — total daily burn, the maintenance line for eating to lose, hold or gain. If you want the number most calorie plans are built on, that’s the one you want. Go to the TDEE calculator →
FAQ
What is BMR?
BMR — Basal Metabolic Rate — is the energy your body spends at complete rest just to stay alive: breathing, circulation, keeping your organs and cells running. It’s the floor of your daily burn, before any movement. Most people’s BMR is the largest single part of the calories they use in a day.
How is BMR calculated?
A formula estimates resting burn from sex, weight, height and age — or from lean mass if you know your body-fat percentage (Katch–McArdle). Because the published equations disagree, we run five (Mifflin–St Jeor, both Harris–Benedict versions, WHO/FAO and Katch–McArdle) and show the spread as a range instead of one number.
What is the difference between BMR and TDEE?
BMR is your burn at complete rest. TDEE — Total Daily Energy Expenditure — is that resting burn multiplied by how active you are, so it includes walking, work and exercise. TDEE is the maintenance line most people actually want; BMR is the resting floor it’s built on.
Which BMR formula is most accurate?
For most people Mifflin–St Jeor tracks measured resting burn slightly better than the older Harris–Benedict equations, and Katch–McArdle can be closer if you know your body-fat percentage because it uses lean mass. But all sit within a few percent of each other — which is why we show the range, not a single “best” one.
How accurate is a BMR calculator?
BMR equations are typically within about ±5–10% for most people. Body composition, thyroid function, medication and age all shift real resting burn, so any single figure can be off by a hundred calories or more. Read the range as a starting point, not a measurement.