Resting Metabolic Rate Calculator
Estimate the calories your body burns at rest each day with Mifflin-St Jeor, Harris-Benedict, Cunningham, Katch-McArdle, Owen and Schofield side by side, compare a lab-measured RMR, and see your daily burn at six activity levels.
How it works
Mifflin-St Jeor: RMR = 10·kg + 6.25·cm − 5·age + s (s = +5 male, −161 female) · Cunningham: 500 + 22·LBM · Katch-McArdle: 370 + 21.6·LBM · Owen: 879 + 10.2·kg (men), 795 + 7.18·kg (women) · Harris-Benedict and Schofield as listed below
Resting metabolic rate is the energy your body uses at rest to run basic functions — breathing, circulation, temperature and cell repair. It typically accounts for 60–75% of total daily calories. The calculator runs seven published equations and lets you choose which one leads. Mifflin-St Jeor (1990) is the default because reviews found it the most accurate of the common equations for the general population. The revised Harris-Benedict (1984) and the original 1919 version are older and usually read a little higher. Cunningham (500 + 22 × lean mass) and Katch-McArdle (370 + 21.6 × lean mass) ignore age and sex and work from lean body mass, so they suit athletes who know their body fat; leave body fat at 0 to estimate lean mass with the Boer formula. Owen uses weight alone, and Schofield — the basis of the WHO equations — uses weight within age bands, which makes it the only one here valid for children. If you have had a metabolic test, enter the measured value to see how far it sits from the prediction; the activity table then uses your measured number. RMR and basal metabolic rate (BMR) are measured under slightly different conditions but are close enough that the same equations are used for both.
Worked example
A 30-year-old man weighing 70 kg at 175 cm: Mifflin-St Jeor gives 10×70 + 6.25×175 − 5×30 + 5 = 1,649 kcal a day (68.7 kcal per hour, 6,898 kJ). The revised Harris-Benedict equation gives 1,696 kcal and Owen 1,593 kcal. At 15% body fat his lean mass is 59.5 kg, so Cunningham gives 500 + 22×59.5 = 1,809 kcal. If a lab test measured 1,750 kcal, that is 6.1% above the Mifflin prediction — within the usual 10%.
Sources: Mifflin MD et al. — A new predictive equation for resting energy expenditure · Frankenfield D et al. (2005) — Comparison of predictive equations for resting metabolic rate · Roza AM, Shizgal HM (1984) — The Harris Benedict equation reevaluated · FAO/WHO/UNU — Human energy requirements (Schofield equations)
Frequently asked questions
What is the difference between RMR and BMR?
They measure nearly the same thing — energy burned at rest. BMR is measured under strict conditions (fully rested, fasted, on waking), while RMR is measured under slightly less strict conditions and comes out marginally higher. The same prediction equations are used for both.
How do I get my total daily calories from RMR?
Multiply RMR by an activity factor, from about 1.2 for sedentary to 1.9 for very active. The table under the result does this for six activity levels. That total, not RMR alone, is what you compare food intake against for weight goals.
Which RMR equation is most accurate?
For most adults, Mifflin-St Jeor, which predicts within 10% of a measured value for most people in validation studies. Cunningham is often closer for lean, muscular athletes when body fat is known. Schofield is the one to use for children.
How accurate is the estimate?
Equations are accurate to within about 10% for most people, but individual metabolism, body composition, hormones and genetics vary. For precise figures, indirect calorimetry (measuring oxygen use) is the clinical standard — enter that result in the measured RMR box to compare.
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Educational estimate only — not medical advice, and not a substitute for a clinician, pharmacist or product label. Dosing, fluid and kidney decisions must be confirmed by a qualified professional using the actual drug, patient and situation. Do not use this tool to self-treat.