How TDEE Calculator works
Methodology for the TDEE Calculator: formulas, coefficients, data sources, assumptions, and known limitations.
Scope
Estimates Total Daily Energy Expenditure by computing Mifflin-St Jeor BMR and multiplying by an activity factor between 1.2 (sedentary) and 1.9 (athlete).
TDEE is the daily calorie ledger a nutrition plan is written against. Treat the output as a starting point, not a precise metabolic measurement.
Formula
BMR (men) = 10*weight_kg + 6.25*height_cm - 5*age + 5. BMR (women) = 10*weight_kg + 6.25*height_cm - 5*age - 161. TDEE = BMR x activity_factor.
Coefficients
| Parameter | Value | Note |
|---|---|---|
| Weight coefficient | 10 kcal/kg | |
| Height coefficient | 6.25 kcal/cm | |
| Age coefficient | -5 kcal/year | |
| Sex constant (male / female) | +5 / -161 | |
| Activity factor — sedentary | 1.2 | |
| Activity factor — light | 1.375 | |
| Activity factor — moderate | 1.55 | |
| Activity factor — very active | 1.725 | |
| Activity factor — athlete | 1.9 |
Data sources
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. — PMID 2305711. The most accurate of the common BMR predictors for non-obese adults.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789. — PMID 15883556. Meta-analysis identifying Mifflin-St Jeor as the most accurate predictor.
- Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808-812. — PMID 34385400. Multi-country doubly-labeled-water dataset used to validate the activity-factor bands.
Assumptions
- User inputs metric or imperial units correctly; the tool converts internally.
- Chosen activity factor matches real-world training and occupational load; 'moderate' regularly over-states true activity for office workers who lift 3x/week.
- Lean-mass differences between individuals are not adjusted for (Katch-McArdle is a separate path).
Approximation range
Mifflin-St Jeor RMSE vs indirect calorimetry is typically 150–200 kcal/day for healthy non-obese adults. For obese populations the error widens and Katch-McArdle or DXA-derived LBM performs better.
Activity factors are bucketed; real daily expenditure often falls between two buckets, giving an inherent +/- 10% band.
Limitations
- Does not model NEAT adaptations during large deficits, which can shave 10–20% off predicted expenditure within weeks.
- Single-point estimate — does not track week-to-week weight trend that a calibrated nutrition plan should use.
- Ignores thyroid status, medications, and pregnancy.
Reproducibility
Male, 85 kg, 180 cm, 30 yrs, moderate activity: BMR = 10*85 + 6.25*180 - 5*30 + 5 = 1830 kcal. TDEE = 1830 * 1.55 = 2836 kcal.
Change log
- 2026-04-24: methodology page first published.
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