Methodology
Every calculator on FitCalcLab uses a published, peer-reviewed equation. We cite the source on each tool's page and do not tune the formulas. This page explains how the tools are built, reviewed and kept current.
Reviewed by the FitCalcLab Editorial Team · Updated 2026-08-01
Formulas we use
- TDEE uses the Mifflin-St Jeor equation (Am J Clin Nutr, 1990) with standard activity multipliers from 1.2 to 1.9.
- Macros convert calories to grams with the Atwater factors: 4 kcal/g protein and carbs, 9 kcal/g fat.
- One-rep max reports the Epley and Brzycki estimates and their average.
- BMI uses the WHO definition (kg/m²) with the WHO adult cut-offs.
- Body fat uses the U.S. Navy circumference method (Hodgdon & Beckett, 1984).
How we review
The formulas and copy are reviewed by the FitCalcLab Editorial Team, who work in sports science and nutrition. We re-check sources and update the tools when guidance changes.
Limits
These tools give estimates for healthy adults and do not replace medical advice. Speak to a qualified professional before changing your diet or training.