Resting Metabolic Rate (RMR) Calculator

Calculate your Resting Metabolic Rate using the Mifflin-St Jeor equation. Estimate daily calorie needs at different activity levels.

One equation does all the work: Mifflin-St Jeor, which weights each kilogram at 10 kcal, each centimetre at 6.25 kcal and each year of age at minus 5 kcal, then adds 5 for men or subtracts 161 for women. A 30-year-old man of 70 kg and 175 cm lands at 1,649 kcal a day, and the same profile as a woman lands at 1,483 — a flat 166 kcal gap that never varies with size. Which input matters most depends on how you ask. Per unit, weight is the heaviest term, 10 kcal against 6.25 for height, so a kilogram gained is worth more than a centimetre gained. Per realistic variation, height wins, because heights are numerically larger: a ten percent difference in stature is 17.5 cm and moves the result by 219 kcal, while ten percent of body weight is 7 kg and moves it by 140. Age is the weakest lever by either measure, costing just 5 kcal a year, which is why the equation predicts a modest decade-to-decade decline of 50 kcal. The four TDEE rows are the same number multiplied by activity factors of 1.2, 1.375, 1.55 and 1.725 — the bottom row carries the Very Active label at the 1.725 factor, and the accompanying chart adds a fifth 1.9 bar for extra-active athletes that has no matching output row. Resting rate is not measured here; predictive equations sit within about ten percent of indirect calorimetry for most adults and drift further for the very lean, the very heavy and the elderly.