Resting Metabolic Rate Msj
Calculator

It estimates resting metabolic rate (RMR), the calories your body burns at complete rest to maintain basic physiological functions, using weight, height, age, and sex. It's widely regarded as one of the more accurate predictive equations for RMR in the general population.

Mifflin-St Jeor was developed later using more modern body composition measurement techniques and is generally considered more accurate for today's population, especially for people with overweight or obesity, where Harris-Benedict tends to overestimate. Most nutrition professionals now default to Mifflin-St Jeor over Harris-Benedict.

Men typically carry more lean muscle mass at a given weight than women, and since muscle tissue burns more calories at rest than fat tissue, the equation applies a different constant by sex to account for this difference in body composition. Using the wrong sex input skews the RMR estimate.

No, RMR only reflects calories burned at complete rest; total daily calories burned also include movement, exercise, and the energy used to digest food, which is why RMR is typically multiplied by an activity factor to estimate total daily expenditure.

It's typically within about 10% of measured RMR for most people, which is quite good for a predictive equation, though individual variation in muscle mass, hormones, and genetics can push some people further from the estimate. Indirect calorimetry testing remains the gold standard when precision matters.