BMR Calculator
Basal metabolic rate by three formulas, side by side.
Optional. Supplying it unlocks Katch-McArdle, the most accurate of the three.
BMR (Mifflin-St Jeor)
1,649 kcal
at complete rest, before any activity
BMR excludes all movement and digestion. Never use it as a calorie target — that comes from TDEE.
How the BMR Calculator works
Basal metabolic rate is what your body spends doing nothing at all — running your heart, brain, kidneys and cell repair while you lie still. It is 60 to 70 percent of most people's daily burn, and it is the floor every other calorie figure is built on.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
Which BMR formula is most accurate?
Mifflin-St Jeor is the current standard and lands within about 10% for most adults. Harris-Benedict, published in 1919 and revised in 1984, tends to read high. Katch-McArdle is the most accurate of the three but needs your body fat percentage, because it works from lean mass rather than total weight.
Why do the three formulas give different answers?
They were derived from different populations at different times. Harris-Benedict came from a small early-20th-century sample; Mifflin-St Jeor from a larger, more modern and more varied one. Katch-McArdle sidesteps the problem by measuring what actually burns energy — lean tissue — rather than inferring it from height and weight.
Can I change my BMR?
Somewhat, and slowly. More lean mass raises it, since muscle is metabolically active at rest. Prolonged aggressive dieting lowers it, partly through lost tissue and partly through adaptation. The day-to-day swings people attribute to a fast or slow metabolism are usually differences in activity, not BMR.
Should I eat at my BMR to lose weight?
No. BMR excludes all movement, digestion and exercise, so eating at it creates a much larger deficit than the number suggests. Diet targets are set from TDEE — BMR multiplied by an activity factor — not from BMR itself.