How our calculators work
Everything here is computed in your browser with published, peer-reviewed equations. No magic, no dark patterns, no hidden data collection.
BMR equations
| Equation | Formula (kcal/day) | Notes |
|---|---|---|
| Mifflin-St Jeor (default) | 10·kg + 6.25·cm − 5·age + 5 (men) / −161 (women) | Most accurate of the population equations |
| Katch-McArdle | 370 + 21.6·LBM | Requires body fat %; LBM = mass × (1 − BF%) |
| Cunningham | 500 + 22·LBM | Lean-mass alternative; requires body fat % |
| Harris-Benedict (Revised) | 88.362 + 13.397·kg + 4.799·cm − 5.677·age (men); 447.593 + 9.247·kg + 3.098·cm − 4.330·age (women) | Historical comparison |
Mifflin et al., 1990, PMID 2305711.
Activity multipliers
| Tier | Factor | Meaning |
|---|---|---|
| Sedentary | 1.2 | Desk job, no structured exercise |
| Light | 1.375 | 1–3 days/week light activity |
| Moderate | 1.55 | 3–5 days/week training |
| Heavy | 1.725 | 6–7 days/week hard training |
| Athlete | 1.9 | Two-a-days or physical labor |
Goal adjustments and macros
| Goal | Daily target | Macro split |
|---|---|---|
| Cut | TDEE − 500 | Protein 40% · Carbs 30% · Fat 30% |
| Maintain | TDEE | Protein 30% · Carbs 40% · Fat 30% |
| Bulk | TDEE + 500 | Protein 30% · Carbs 45% · Fat 25% |
Grams convert as: protein and carbs = 4 kcal/g, fat = 9 kcal/g.
Known error and expectations
- Set the honest ±10% expectation: a 2,300 kcal-day target could be off by ~230 kcal.
- Validated against indirect calorimetry in the source studies; individual metabolism varies.
- We recommend treating the first number as a hypothesis and adjusting ±100 kcal/day against a 7-day moving average.
Privacy by design
All math runs client-side in vanilla JavaScript. No cookies, no analytics, no server-side inputs; nothing about your body is ever sent over the network.