What BMR tells you
Basal Metabolic Rate is the energy cost of simply being alive — heartbeat, breathing, brain function, cell turnover — measured at complete rest. For most people it's 60–70% of everything they burn in a day.
BMR is not an eating target. It's the floor your TDEE is built on: multiply it by an activity factor to get the number that actually guides your intake. Eating at or below BMR for extended periods is a sign your plan is too aggressive.
Why three formulas?
Each equation was fit to different reference data. Mifflin-St Jeor (1990) is the modern default; Harris-Benedict (1919, revised 1984) tends to read slightly high today; Katch-McArdle ignores age and sex and works purely from lean body mass — often the best pick for lean, muscular people, if you can supply a decent body-fat estimate.
Frequently asked questions
What is a normal BMR?
Roughly 1,200–1,600 kcal/day for adult women and 1,500–2,000 for adult men, scaling primarily with body size and lean mass. Outliers usually have unusually high or low lean mass rather than a 'fast' or 'slow' metabolism.
Should I eat at my BMR to lose weight?
Generally no. BMR ignores all daily activity, so eating at BMR usually creates an unnecessarily harsh deficit. Calculate TDEE and subtract a controlled amount instead.
Can I increase my BMR?
Meaningfully, in one way: build muscle. Each kilogram of muscle adds roughly 13 kcal/day at rest — modest per kg, but the training that builds it burns far more.
More calculators
TDEE Calculator
Work out your Total Daily Energy Expenditure
Calorie Calculator
Get a daily calorie target matched to your goal
Calorie Deficit Calculator
Choose a weekly weight-loss rate and see the exact daily calories that achieve it
Macro Calculator
Split your daily calories into protein, carbs and fat
Maintenance Calorie Calculator
Find the daily calories that keep your weight stable
Weight Loss Calculator
See your realistic goal date
Sources
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990. [link]
- Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. PNAS. 1918. [link]
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984. [link]
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. Wolters Kluwer.