About RepMaths

RepMaths builds fast, free calculators for lifters and fitness enthusiasts — one-rep max, training percentages, body composition, nutrition, and more. No sign-up, no clutter, just accurate numbers you can use right away.

Methods & Formulas We Use

Every calculator on this site is built on established, published formulas and methods from strength training and exercise science — never anything we invented ourselves. We name the exact method used on each tool page so you can verify it independently.

Strength & 1RM Estimation

• Epley Formula
• Brzycki Formula
• Lander Formula
• Lombardi Formula

Training & Load Management

• RPE (Rate of Perceived Exertion) scale
• RIR (Reps in Reserve) method
• Training Max methodology (as used in 5/3/1-style programming)

Strength Comparison

• Wilks Coefficient
• DOTS Score

Body Composition

• U.S. Navy Body Fat Method (Hodgdon & Beckett, 1984)
• Body Mass Index (BMI / Quetelet Index)
• Devine and Robinson ideal body weight formulas

Nutrition & Energy Expenditure

• Mifflin-St Jeor Equation
• Harris-Benedict Equation
• Katch-McArdle Formula
• Standard TDEE activity multipliers

All calculators provide estimates for educational purposes and are not a substitute for professional medical, nutritional, or fitness advice. See our Disclaimer for more details.