how to calculate 1RM without testing
Testing a true 1RM is tiring, technique-heavy and risky. The alternative is a submaximal set to failure (for example 5 reps) and an empirical formula. The calculator below uses seven of them and shows the average and the range.
The average is 115.5 kg and the range runs from 112.5 to 119.0 kg, about 5.6% of the average. For planning, a 1RM of about 115 kg is a reasonable guess.
At 8 reps the formulas already spread from 96.0 (O'Conner) to 102.1 kg (Wathan): that is why the range matters more than a single value.
At 10 reps Epley and Brzycki coincide exactly (60 x 4/3 = 80). Above that Brzycki gives larger values, and the estimate's confidence is only moderate.
It is the heaviest load you can lift for a single full repetition with correct technique in a given exercise. It is a reference for dosing training in percentages, not a goal and not something you are obliged to test.
Between 3 and 8 reps to failure, with good technique, usually give the best balance of safety and accuracy. With 1 rep you already have the 1RM, and with more than 10 the estimate loses a lot of reliability.
The formulas assume the set ended at failure. If you had reps left, your real 1RM is higher than estimated. In that case use the RPE tab, which corrects the calculation for the reps you had in reserve.
No. The 1RM is specific to each exercise and variation (flat bench, incline, free squat, machine). Calculate one for each movement you want to dose.
| Formula | 1RM (kg) |
|---|---|
| Epley | 116.7 |
| Brzycki | 112.5 |
| Lander | 113.7 |
| Lombardi | 117.5 |
| Mayhew | 119 |
| O'Conner | 112.5 |
| Wathan | 116.6 |
Each formula is a regression fitted to specific groups and lifts, so the values differ. Averaging the seven reduces the bias of any one, but does not remove the error.
The fraction of 1RM each formula assigns to each rep count. They agree closely at low reps and drift apart as reps grow.
| Reps | Epley | Brzycki | Lander | Lombardi | Mayhew | O'Conner | Wathan |
|---|---|---|---|---|---|---|---|
| 1 | 100% | 100% | 100% | 100% | 100% | 100% | 100% |
| 2 | 93.8% | 97.2% | 96% | 93.3% | 89.7% | 95.2% | 95.1% |
| 3 | 90.9% | 94.4% | 93.3% | 89.6% | 87.7% | 93% | 91.8% |
| 4 | 88.2% | 91.7% | 90.6% | 87.1% | 85.8% | 90.9% | 88.7% |
| 5 | 85.7% | 88.9% | 87.9% | 85.1% | 84% | 88.9% | 85.8% |
| 6 | 83.3% | 86.1% | 85.3% | 83.6% | 82.3% | 87% | 83.1% |
| 8 | 78.9% | 80.6% | 79.9% | 81.2% | 79.2% | 83.3% | 78.3% |
| 10 | 75% | 75% | 74.6% | 79.4% | 76.4% | 80% | 74.2% |
| 12 | 71.4% | 69.4% | 69.2% | 78% | 73.9% | 76.9% | 70.7% |
| 15 | 66.7% | 61.1% | 61.2% | 76.3% | 70.6% | 72.7% | 66.3% |
This is a mathematical estimate, not a real test or a training prescription. Only attempt a true 1RM with good technique, a warm-up, safety pins or a spotter, ideally under professional supervision. If you have an injury or a health condition, talk to a professional first.