🍽️ BMR and Caloric Needs

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · Checked against 2 independent reference calculations · how PhDino checks its numbers

Estimating resting energy expenditure and total daily calorie needs from body measurements and activity level.

Basal metabolic rate is the energy the body uses just to maintain basic life functions at complete rest — breathing, circulation, cell repair, and so on — before any activity is added on top. It's estimated (not directly measured, which requires specialized equipment) from weight, height, age, and sex, since these correlate reasonably well with actual measured metabolic rate across a population.

The Mifflin-St Jeor equation used here is one of several BMR estimation formulas developed over the decades (the older Harris-Benedict equation is another commonly seen one) — Mifflin-St Jeor is generally regarded as more accurate for most of the modern population than the older formulas it superseded.

Total daily energy expenditure scales BMR up by an activity multiplier to estimate actual daily calorie needs, since a sedentary day and a physically demanding one burn very different amounts of energy on top of the same resting baseline.

Key formula

Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
TDEE = BMR × activity multiplier

Notes & limitations

• This is a population-average estimate, not an individual metabolic measurement — actual metabolic rate varies meaningfully between individuals of the same weight, height, age, and sex due to factors like muscle mass and genetics that the formula doesn't capture.
• Activity multiplier categories are necessarily approximate — real activity levels form a continuum, not five discrete buckets, so the chosen category is itself an estimate layered on top of the BMR estimate.