Methodology & Sources
Every GymCalc calculator uses a widely accepted, published formula. Here is what powers each calculation and where the method comes from. Results are estimates and are not a substitute for professional advice.
Body composition
| Body Mass Index (BMI) & categories | World Health Organization — BMI classification (kg/m²). |
| Body fat — US Navy circumference method | Hodgdon & Beckett, Naval Health Research Center, 1984. |
| Lean body mass — Boer formula | Boer P., Am J Physiol, 1984. |
| Fat-Free Mass Index (FFMI) | Kouri et al., Clin J Sport Med, 1995 (normalised to 1.8 m). |
| Waist-to-hip ratio & risk bands | World Health Organization waist-to-hip thresholds. |
| Ideal body weight (4 formulas) | Devine 1974, Robinson 1983, Miller 1983, Hamwi 1964. |
Energy & nutrition
| BMR & TDEE — Mifflin-St Jeor + activity factors | Mifflin, St Jeor et al., Am J Clin Nutr, 1990. |
| Harris-Benedict (revised) & Katch-McArdle | Roza & Shizgal, Am J Clin Nutr, 1984; Katch & McArdle. |
| Calorie deficit → fat loss | Energy balance: ≈7,700 kcal per kg of body fat. |
| Macronutrients & protein targets | ISSN position stand (Jäger et al., 2017): 1.6–2.2 g protein/kg. |
Strength
| One-rep max (1RM) estimates | Epley 1985, Brzycki 1993, Lombardi 1989 (averaged). |
| Wilks score | Wilks coefficient (R. Wilks), classic powerlifting formula. |
| Barbell plate loading | Deterministic greedy loading; IWF plate colours. |
Cardio
| Max heart rate & training zones | Tanaka et al., J Am Coll Cardiol, 2001 (208 − 0.7×age); Karvonen reserve method. |
| Calories burned (MET values) | Ainsworth et al., Compendium of Physical Activities, 2011. |
| Running pace, speed & finish times | Distance/time; constant-pace projection. |
Primary sources are cited by author and year of publication. The calculators implement these formulas directly; the calculation logic is transparent and verifiable.