Method
Formulas & sources
No house formulas. Each calculator uses a published equation or reference value, listed here with where it came from and which tools use it.
| Quantity | Method | Source | Used in |
|---|---|---|---|
| Basal metabolic rate | Mifflin-St Jeor | Mifflin MD, St Jeor ST, et al. Am J Clin Nutr 1990;51:241–247 | BMR, TDEE, deficit, macro, goal date |
| Basal metabolic rate | Harris-Benedict (revised) | Roza AM, Shizgal HM. Am J Clin Nutr 1984;40:168–182 | BMR |
| Basal metabolic rate | Katch-McArdle | McArdle, Katch & Katch, Exercise Physiology | BMR (with body fat %) |
| Activity | Multipliers 1.2–1.9 | FAO/WHO/UNU Human energy requirements, 2004 (physical activity levels) | TDEE, deficit, macro, goal date |
| Weight change | ≈7,700 kcal per kg | Classic approximation; dynamics per Hall KD et al. Lancet 2011 | Deficit, goal date |
| Body fat | U.S. Navy circumference method | Hodgdon JA, Beckett MB. Naval Health Research Center, 1984 | Body fat |
| Body mass index | kg/m², WHO adult categories | WHO Technical Report Series 894, 2000 | BMI |
| Protein | 0.8 g/kg RDA; 1.6–2.2 g/kg for muscle gain | Institute of Medicine 2005; Morton RW et al. Br J Sports Med 2018 | Protein |
| Water | 3.7 L men / 2.7 L women total water | Institute of Medicine, DRIs for Water, 2005 | Water intake |
| Macros | 4 / 4 / 9 kcal per gram | Atwater factors (USDA) | Macro |
What the calculators do not do
They do not diagnose anything, and they are designed for healthy adults. Pregnancy, breastfeeding, growing children, kidney disease, diabetes treatment and a history of disordered eating all change the picture; in those cases, ask a clinician.
Privacy of your inputs
Calculations run in your browser. Nothing you type is stored or sent to us.
Corrections
If you spot an error in a formula or a source, it gets fixed and noted here with the date. No corrections yet (site launched October 22, 2026).