O'Conner One-Rep Max Calculator
Apply the O'Conner equation to estimate 1RM from moderate rep sets. This variation offers a slightly conservative projection than Epley.
Enter Your Lift
Designed for moderate rep ranges where you maintain good form.
Results
Estimated One-Rep Max
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70 percent 1RM
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80 percent 1RM
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90 percent 1RM
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How the O'Conner Formula Works
Formula
1RM = weight x (1 + 0.025 x reps)
Step-by-step
- Multiply the completed reps by 0.025.
- Add 1 to that product to find the adjustment factor.
- Multiply the weight lifted by the factor to estimate your one-rep max.
Notes
This formula was originally used in military settings and gives a slightly lower estimate than Epley at similar rep counts, making it a conservative option.