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ToolWrenEstimate your Basal Metabolic Rate and daily calorie needs based on your age, sex, height, weight and activity level.
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BMR is a free, private online tool that lets you estimate your Basal Metabolic Rate (BMR) and daily calorie needs with the Mifflin-St Jeor equation. It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
Basal Metabolic Rate is the energy your body uses at complete rest to keep you alive — breathing, circulation and cell function. It is the foundation of your daily calorie needs.
This tool uses the Mifflin-St Jeor formula, widely regarded as one of the most accurate predictive equations for BMR.
Your maintenance calories are BMR multiplied by an activity factor, from sedentary (1.2) to very active (1.9). Eat below maintenance to lose weight, above to gain.
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to stay alive — powering your heart, lungs, brain and cell repair. It typically accounts for 60–70% of your total daily energy use, which makes it the foundation for understanding how many calories you need to maintain, lose or gain weight.
This calculator uses the Mifflin-St Jeor equation, widely regarded as one of the most accurate predictive BMR formulas for the general population. It estimates BMR from your weight, height, age and sex. It superseded the older Harris-Benedict equation because studies showed it predicts real resting metabolism more reliably for most people.
BMR is what you burn at rest, but you also move. Multiplying BMR by an activity factor — from 1.2 for sedentary up to 1.9 for very active — gives your Total Daily Energy Expenditure (TDEE), the calories needed to maintain your current weight. Eat below TDEE to lose weight and above it to gain; this tool shows maintenance plus mild loss and gain targets.
Each input changes metabolism. More body mass (especially muscle) burns more at rest. Men generally have higher BMR than women due to body composition. BMR declines gradually with age. Taller, heavier and younger bodies therefore tend to have higher BMRs — which is why a one-size-fits-all calorie number is misleading and a personalised estimate is more useful.
These are statistical estimates; real metabolism varies with genetics, muscle mass, hormones and health conditions. Use the figure as a sensible starting point, track how your weight responds over a couple of weeks, and adjust. For medical or performance nutrition, consult a professional. Everything is calculated in your browser.