BMR Calculator

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest, before any activity is factored in. We use the same Mifflin-St Jeor equation that powers our TDEE calculator, since BMR is the first step of that calculation — it's widely regarded as the most accurate predictive formula for resting energy expenditure in healthy adults.

Two people with the same height and weight can still land on meaningfully different BMRs. A few factors drive most of that spread:

Age. BMR declines gradually over adulthood, driven mainly by a slow loss of lean muscle mass and shifting hormone levels rather than aging itself. Mifflin-St Jeor already bakes this in as a per-year age term, so the number above has this adjustment built in — you don't need to apply it again.

Sex. At the same height and weight, men typically post a higher BMR than women, mostly because men carry more lean muscle mass and less body fat on average. That's why the equation uses a separate constant for male vs. female rather than one formula for everyone.

Muscle mass. Muscle tissue is more metabolically active at rest than fat tissue, so two people at an identical weight but different body composition can have genuinely different BMRs even when a formula predicts the same number for both. Mifflin-St Jeor only sees height, weight, age, and sex — it has no way to know your actual muscle-to-fat ratio, which is a big part of why this is a population-average estimate rather than a measurement of you specifically.