Seven published equations turn a set of reps into an estimated one rep max. Here they all get the same input, 100 kg lifted for 1 to 12 reps, computed with the same code as the one rep max calculator.
The comparison
| Reps | Epley | Brzycki | Lander | Lombardi | Mayhew | O’Conner | Wathen | Spread |
|---|---|---|---|---|---|---|---|---|
| 1 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 |
| 2 | 106.7 | 102.9 | 104.2 | 107.2 | 111.4 | 105.0 | 105.1 | 8.6 |
| 3 | 110.0 | 105.9 | 107.2 | 111.6 | 114.0 | 107.5 | 109.0 | 8.1 |
| 4 | 113.3 | 109.1 | 110.4 | 114.9 | 116.5 | 110.0 | 112.8 | 7.4 |
| 5 | 116.7 | 112.5 | 113.7 | 117.5 | 119.0 | 112.5 | 116.6 | 6.5 |
| 6 | 120.0 | 116.1 | 117.3 | 119.6 | 121.5 | 115.0 | 120.3 | 6.5 |
| 7 | 123.3 | 120.0 | 121.1 | 121.5 | 123.9 | 117.5 | 124.0 | 6.5 |
| 8 | 126.7 | 124.1 | 125.1 | 123.1 | 126.3 | 120.0 | 127.7 | 7.7 |
| 9 | 130.0 | 128.6 | 129.4 | 124.6 | 128.6 | 122.5 | 131.2 | 8.7 |
| 10 | 133.3 | 133.3 | 134.1 | 125.9 | 130.9 | 125.0 | 134.7 | 9.7 |
| 11 | 136.7 | 138.5 | 139.1 | 127.1 | 133.2 | 127.5 | 138.2 | 12.0 |
| 12 | 140.0 | 144.0 | 144.4 | 128.2 | 135.4 | 130.0 | 141.5 | 16.2 |
Every formula scales with the weight, so for 60 kg multiply each number by 0.6, for 225 lb by 2.25 (and read the result in lb).
What the table shows
- At 1 rep, every formula gives the weight itself. The calculator sets it that way: a single rep is already a one rep max.
- The spread is smallest at 5 to 7 reps, 6.5 kg, and grows on either side: 8.6 kg at 2 reps and 16.2 kg at 12 reps. At 2 reps Mayhew's curve already reads 111.4 kg while Brzycki reads 102.9 kg.
- Epley and Brzycki meet at exactly 10 reps (133.3 kg). Below 10, Epley reads higher; above 10, Brzycki does.
- Lombardi flattens out. Its power curve (reps to the power 0.1) grows more and more slowly, so it is among the highest at low reps and the lowest from 11 reps on.
- The lowest estimate changes with the reps. Brzycki is lowest from 2 to 4 reps, ties with O'Conner at 5, and O'Conner (2.5% per rep) is lowest from 6 to 10.
Which formula is best?
It depends on the lift and the lifter. Ribeiro and colleagues (2024) tested nine equations on 119 young men and women before and after a training program. Lombardi came closest for men in the bench press and squat; Brown, Brzycki and Lander were closest for women in those lifts; and for the arm curl, all equations missed for men. A 2010 bench press study in Motricidade found no significant difference between six equations and the tested 1RM in 31 recreational lifters doing 4 to 10 reps.
That is why the calculator shows the Epley-Brzycki average as its main number and the range of all seven next to it. The coefficients for Lander, Lombardi, Mayhew, O'Conner and Wathen are the ones printed in Ribeiro and colleagues' Table 1.