What is the Mayhew Formula?
Formula
1RM = (100 × Weight) ÷ (52.2 + 41.9 × e^(-0.055 × Reps))
The Mayhew et al. formula was developed in 1992 and is designed to be more accurate for higher rep ranges (8+ reps) where fatigue becomes a more significant factor in performance.
Example Calculation:
If you can deadlift 315 lbs for 5 reps:
1RM = (100 × 315) ÷ (52.2 + 41.9 × e^(-0.055 × 5))
1RM = 31500 ÷ (52.2 + 41.9 × e^(-0.275))
1RM = 31500 ÷ (52.2 + 41.9 × 0.7596)
1RM = 31500 ÷ (52.2 + 31.8)
1RM = 31500 ÷ 84.0
1RM = 375.0 lbs (170.1 kg)
1RM = 31500 ÷ (52.2 + 41.9 × e^(-0.275))
1RM = 31500 ÷ (52.2 + 41.9 × 0.7596)
1RM = 31500 ÷ (52.2 + 31.8)
1RM = 31500 ÷ 84.0
1RM = 375.0 lbs (170.1 kg)
Why Use Mayhew?
- Higher rep accuracy: Better for 8+ rep sets
- Research-based: Validated in scientific studies
- Fatigue factor: Accounts for cumulative fatigue
- Endurance training: Good for higher rep programs