BMR formulas

Mifflin–St Jeor (default)

Men:   BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161

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 Feb;51(2):241-7. PMID: 2305711.

Harris–Benedict (revised, 1984)

Men:   BMR = 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
Women: BMR = 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)

Roza AM, Shizgal HM. The Harris Benedict equation re-evaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984 Jul;40(1):168-82. PMID: 6741850.

Katch–McArdle

BMR = 370 + (21.6 × LBM kg)

Katch FI, McArdle WD. Nutrition, Weight Control, and Exercise. Lea & Febiger; 1977 (and subsequent editions of Exercise Physiology).

Cunningham

BMR = 500 + (22 × LBM kg)

Cunningham JJ. Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. Am J Clin Nutr. 1991 Dec;54(6):963-9. PMID: 1985388.

Body composition formulas

BMI: weight(kg) / height(m)². WHO standard
LBM (Boer): Men: 0.407 × kg + 0.267 × cm − 19.2; Women: 0.252 × kg + 0.473 × cm − 48.3 (Boer P. Am J Physiol. 1984;247:F632–F636)
LBM (body fat known): weight × (1 − BF%/100)
Max Fat Metabolism: 31 × pounds of fat per day (commonly attributed to Lyle McDonald based on lipolysis research)
Waist-to-Height Ratio: waist / height; cutoff 0.5 from Ashwell et al. Obes Rev. 2012

TDEE multipliers

Activity multipliers follow the standard published scale:

1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 heavy, 1.9 athlete

This scale appears across the original Harris–Benedict literature and subsequent texts including the FAO/WHO/UNU 1985 and 2001 energy reports.

Macro calculation

protein g = (kcal × protein_fraction) / 4
carbs g   = (kcal × carb_fraction) / 4
fat g     = (kcal × fat_fraction) / 9

Protein floor recommendations: 1.6–2.2 g/kg for muscle preservation/growth (Schoenfeld & Aragon, Nutrients 2018; Helms et al., J Int Soc Sports Nutr 2014).

Life-stage adjustments

Luteal phase +150 kcal: Reed et al., Am J Clin Nutr. 1988; Henry et al. 2001 (energy expenditure in luteal phase)
Pregnancy T1/T2/T3 +0/+340/+452: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. 2002.
Breastfeeding +400 (floor 1,800): WHO & IOM 2002 + AAP breastfeeding policy
Perimenopause −175: Lovejoy JC, Champagne CM, de Jonge L, et al. Int J Obes. 2008;32:949-958.
PCOS −6% BMR: Jakubowicz D, Barnea M, Wainstein J, Froy O. Clin Sci (Lond). 2013;125(9):423-32.

How accurate are these?

Per /how-accurate-is-tdee/: formula-based TDEE estimates miss by more than 250 kcal/day for at least half of users (MacroFactor public dataset, 2024). Treat all numbers from this calculator as starting points and calibrate empirically over 2–3 weeks.

Errata

None reported. If you find an error in any formula or citation, please email [email protected] with the issue and we will fix and credit you here.

Methodology