Free BMR Calculator — Mifflin-St Jeor Basal Metabolic Rate (2026)
Calculate your BMR with the Mifflin-St Jeor equation (and Harris-Benedict for comparison), see your calorie burn at every activity level, and turn the number into a personalized USDA food plan. Free, no signup.
Your basal metabolic rate is the energy your body burns at complete rest — the calories that keep your heart, brain, and lungs running before you take a single step. Enter five details and get your BMR by the two most-cited equations, plus what it means for your daily calories.
What BMR actually measures
Basal metabolic rate is the floor of your energy budget: the calories burned by organ function, cell repair, and temperature regulation while you're fully at rest. For most people it's 60–75% of everything they burn in a day. The rest comes from movement and from digesting food itself.
BMR isn't a goal to eat toward — it's the input for finding your real-life number. Multiply it by an activity factor and you get your total daily energy expenditure (TDEE), which is what maintenance, deficit, and surplus targets are built from.
The equations, in the open
Mifflin-St Jeor (1990): men 10×kg + 6.25×cm − 5×age + 5; women 10×kg + 6.25×cm − 5×age − 161. The American Dietetic Association found it the most reliable of the standard equations for healthy adults, which is why it's our headline number.
Revised Harris-Benedict (1984): men 88.362 + 13.397×kg + 4.799×cm − 5.677×age; women 447.593 + 9.247×kg + 3.098×cm − 4.330×age. Older, still widely used; we show it so you can see how much the choice of equation moves the result.
Formula & sources
Mifflin-St Jeor (headline)
Revised Harris-Benedict (comparison)
W = weight in kg, H = height in cm, A = age in years. Result in kcal/day.
Sources
- Mifflin MD, St Jeor ST, et al. (1990) A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51(2):241–247.
- Roza AM, Shizgal HM (1984) The Harris–Benedict equation reevaluated. Am J Clin Nutr 40(1):168–182.
BMR questions, answered
What is a normal BMR?
Most adults land between roughly 1,200 and 2,000 kcal/day — it scales with body size, drops with age, and runs higher in men on average because of lean-mass differences. There's no single 'good' BMR; it's an input, not a score.
Should I eat at my BMR to lose weight?
No. BMR is what you'd burn in a coma, not a sensible intake. Weight management targets are set against TDEE (BMR × activity). Eating below BMR for extended periods is something to do only under medical supervision.
Why do different calculators give different BMRs?
They use different equations (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) and some quietly apply activity factors. We show two equations explicitly so the spread is visible instead of hidden.
What's the difference between BMR and RMR?
BMR is measured under strict lab conditions (fasted, rested, controlled temperature); RMR (resting metabolic rate) is measured under looser conditions and runs slightly higher. Online calculators, including this one, estimate the BMR/RMR ballpark from the same equations.
Can I increase my BMR?
Mostly through lean mass: muscle tissue burns more at rest than fat tissue, so resistance training nudges BMR up over time. Crash dieting works the other way — large prolonged deficits can suppress it.
How is this different from the MyPlate calorie calculator?
The MyPlate Plan uses the IOM EER equations that USDA food patterns are built on, and answers a different question: not just how much, but what to eat. Your profile carries over with one click.