What is the O'Conner Formula?
Formula
1RM = Weight × (1 + Reps ÷ 40)
The O'Conner formula is very similar to the Epley formula but uses 40 instead of 30 as the divisor. This makes it slightly more conservative, giving lower 1RM estimates.
Example Calculation:
If you can deadlift 315 lbs for 5 reps:
1RM = 315 × (1 + 5 ÷ 40)
1RM = 315 × (1 + 0.125)
1RM = 315 × 1.125
1RM = 354.4 lbs (160.8 kg)
1RM = 315 × (1 + 0.125)
1RM = 315 × 1.125
1RM = 354.4 lbs (160.8 kg)
Compare to Epley: 367.5 lbs - O'Conner gives a more conservative estimate.
Why Use O'Conner?
- Similar to Epley: Familiar format for users
- Conservative estimates: Slightly lower than Epley
- Good middle ground: Between Epley and Brzycki
- Established method: Used in fitness research