RMR (Resting Metabolic Rate) Calculator

RMR: Resting Metabolic Rate

RMR (Resting Metabolic Rate) is the energy your body burns at rest under everyday conditions — similar to BMR, but measured under less strict criteria (no overnight fast, just quiet rest). In practice, RMR ≈ 1.1 · BMR. The Mifflin-St Jeor (1990) equation is the most common: men 10·kg + 6.25·cm − 5·age + 5; women 10·kg + 6.25·cm − 5·age − 161. For athletes with known lean mass, Cunningham is preferred: RMR = 500 + 22·LBM_kg. Example: man, 75 kg, 175 cm, 30 years → Mifflin = 1,699 kcal/day → RMR ≈ 1,870 kcal/day. Same-person variation can reach ~5% across days. For weight loss, a deficit of 300–500 kcal/day roughly equals 0.3–0.5 kg/week.

Applications and context

RMR drives clinical nutrition plans, weight-loss programs, body recomposition, and sports caloric programming. It is preferred over BMR in real-world settings because BMR's strict measurement protocol (12 h fasted, thermoneutral environment, lying down) is rarely feasible. Most "BMR" calculators online actually estimate RMR. Combine RMR with an activity factor (1.2–1.9) to get TDEE.

FAQ

RMR or BMR — what's the difference? BMR is measured under strict conditions (post-sleep, fasted, lying down); RMR is measured at rest under less strict conditions. RMR is roughly 10% higher than BMR.

Which equation should I pick? Mifflin-St Jeor for the general population. Cunningham if you train hard and know your lean mass — it captures muscle's metabolic contribution better.

How big a deficit should I aim for to lose weight? 300–500 kcal/day below TDEE is the sustainable range — about 0.3–0.5 kg per week, mostly fat with preserved muscle when paired with resistance training and adequate protein.