RMR Calculator
Your resting metabolic rate (RMR) is the calories your body burns just keeping you alive — typically 1,300–1,900 kcal a day for adults. This calculator uses the Mifflin-St Jeor equation, the best-validated formula for healthy adults.
Example: with Sex Male · Age (years) 35 · Weight (lb) 170 · Height (feet) 5 · Height (inches) 8 → Resting metabolic rate: 1,681 kcal/day.
Computed by the calculator below using its default values. Change any input to see your own numbers.
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Check it outHow many calories do you burn doing nothing?
More than most people guess. A 35-year-old man, 5 ft 8 in and 170 lb, has an RMR of about 1,681 kcal per day — the energy cost of his heart, brain, breathing, and cell turnover before a single step. The Mifflin-St Jeor equation behind that number is 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, with −161 replacing the +5 for women (a woman with the same stats: about 1,515 kcal).
RMR vs BMR: the two are often used interchangeably, but BMR is measured under strict lab conditions (overnight fast, complete rest, controlled temperature), while RMR is taken under looser resting conditions and runs slightly higher. Prediction equations like Mifflin-St Jeor estimate resting energy expenditure, so treat the result as your RMR ≈ BMR baseline — then multiply by an activity factor (1.2 sedentary, 1.55 moderately active) for total daily needs.
How it’s calculated
Mifflin-St Jeor equation: RMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for men, or − 161 for women. Imperial inputs convert exactly: 1 lb = 0.45359237 kg, 1 in = 2.54 cm. The secondary rows multiply RMR by standard activity factors (1.2 sedentary, 1.55 moderate) to estimate total daily calories. Equations estimate lab-measured values within about 10% for most healthy adults.
Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.
Common mistakes
- Eating at your RMR to maintain weight — maintenance is RMR times an activity factor; RMR alone is roughly a starvation-level intake for active people.
- Confusing RMR with TDEE — RMR is resting burn only; total daily energy expenditure adds all movement and digestion on top.
- Trusting the equation with very high muscle mass or obesity — it uses total weight, so it underestimates lean athletes and can overestimate at high body fat.
Frequently asked questions
How many calories do I burn doing nothing all day?
Your RMR: for a 170 lb, 5 ft 8 in, 35-year-old man about 1,681 kcal; for a woman with the same stats about 1,515 kcal. Larger, younger, and taller bodies burn more at rest.
How do I calculate RMR by hand?
Use Mifflin-St Jeor: 10 × weight in kg + 6.25 × height in cm − 5 × age, then add 5 (men) or subtract 161 (women). Example: 10 × 77.1 + 6.25 × 172.7 − 175 + 5 ≈ 1,681 kcal.
What is the difference between RMR and BMR?
BMR is measured under strict laboratory conditions and is slightly lower; RMR is measured at rest under everyday conditions. For planning purposes the two are close enough to use interchangeably.
How does weight change my RMR?
Every kilogram adds 10 kcal per day in the equation, so about 4.5 kcal per pound. Dropping from 200 lb to 170 lb lowers the example RMR from roughly 1,817 to 1,681 kcal per day.
How many calories do I need in total?
Multiply RMR by an activity factor: 1.2 if sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active. The default example needs about 2,017 kcal on a sedentary day.