OConner Formula 1RM Calculator

The O'Conner formula is a simplified linear model that tends to give slightly more conservative 1RM estimates than Epley.

w × (1 + r/40)The O'Conner formula is a simplified linear model that tends to give slightly more conservative 1RM estimates than Epley.

5 reps
One Rep Max
5 reps @ 225lb
253
lb
OConner formula
Estimated One Rep Max
5@225lb
253lb
Using the OConner formula
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Big Four Strength Levels

Strength levels for a 200lb male, age 30 lifting 253lb in each lift type · enter your details.

Rep Max Projections

OConner algorithm

RepsWeight (lb)
1RM253lb
2RM241lb
3RM235lb
4RM230lb
5RM(current)225lb
6RM220lb
7RM215lb
8RM211lb
9RM207lb
10RM202lb
20RM169lb

Percentage Calculator

Based on 253lb estimated max

IntensityWeight (lb)
100%253lb
95%240lb
90%228lb
85%215lb
80%202lb
75%190lb
70%177lb
65%164lb
60%152lb
55%139lb
50%127lb