About RepMaths
RepMaths builds fast, free calculators for lifters and fitness enthusiasts — covering strength, training, equipment, nutrition, and body composition. No sign-up, no clutter, just useful estimates you can use right away.
Our Approach
RepMaths focuses on practical calculators rather than long-form articles. Each tool is designed to answer a specific fitness or strength-training question and provide a clear result with the method, formula, or assumptions used.
Where established formulas or published methods are available, we use those rather than creating our own formulas. The exact method used is identified on the relevant calculator page so users can understand what the result represents.
Methods & Formulas We Use
Strength & 1RM Estimation
- Epley Formula
- Brzycki Formula
- Lander Formula
- Lombardi Formula
Training & Load Management
- RPE (Rate of Perceived Exertion), using the RTS (Reactive Training Systems) RPE chart
- RIR (Reps in Reserve) method
- Training Max methodology used in 5/3/1-style programming
Nutrition & Energy Expenditure
- Mifflin-St Jeor Equation for BMR and TDEE estimation
- Harris-Benedict Equation
- Standard TDEE activity multipliers
- Protein intake ranges informed by the ISSN (International Society of Sports Nutrition) position stand on protein and exercise
- Standard macronutrient calorie values: 4 kcal/g for protein and carbohydrates, and 9 kcal/g for fat
Body Composition
- U.S. Navy Body Fat Method (Hodgdon & Beckett, 1984)
How to Interpret Our Results
Fitness calculations often depend on individual measurements, training status, body composition, and the assumptions built into each formula. For that reason, RepMaths results should generally be treated as estimates or practical starting points rather than exact measurements.
Different formulas can produce different results from the same inputs. When a calculator supports multiple methods, the tool page explains the methods used so you can understand the differences.
Educational Use
RepMaths is designed for educational and informational purposes. Our calculators are not a substitute for professional medical, nutritional, or fitness advice.
For important health, nutrition, or training decisions, consider consulting an appropriately qualified professional. See our Disclaimer for more information.