One-rep max calculator
Estimate the most you could lift for a single rep from a heavier set of several reps, without risking a true max attempt.
Best accuracy for 10 reps or fewer.
Estimated one-rep max
101.3 kg
| % of 1RM | Weight | Typical reps |
|---|---|---|
| 100% | 101.5 kg | 1 |
| 95% | 96.0 kg | 2 |
| 90% | 91.0 kg | 3 to 4 |
| 85% | 86.0 kg | 5 to 6 |
| 80% | 81.0 kg | 7 to 8 |
| 75% | 76.0 kg | 9 to 10 |
| 70% | 71.0 kg | 11 to 12 |
| 65% | 66.0 kg | 13 to 15 |
| 60% | 61.0 kg | 15 to 18 |
| 55% | 55.5 kg | 18 to 20 |
| 50% | 50.5 kg | 20+ |
How it is estimated
This calculator uses the Epley formula: your one-rep max is about the weight multiplied by (1 plus the reps divided by 30). If you lifted 80 kg for 8 reps, the estimate is about 101 kg. The formula is most accurate for sets of 10 reps or fewer.
Treat the number as an estimate. Fatigue, technique and the exercise itself change the result, and it will differ a little between formulas.
Training with percentages
Many programmes are written in percentages of your one-rep max: for example about 85% for sets of around 5 reps, 75% for around 10 reps and 65% for around 15. The table below the result shows the weight at each percentage so you can plan your sets.
Test a one-rep max for real only with a spotter, enough rest and good form, and use your estimate to pick sensible working weights instead.
Questions and answers
- What is a one-rep max?
- Your one-rep max (1RM) is the heaviest weight you can lift once with good form for a given exercise.
- Is it safe to test a one-rep max?
- It carries more risk than lighter sets. An estimate from a set of 3 to 8 reps is a safer way to find your working weights.
- Which formula does this use?
- The Epley formula, which is also what many workout apps use, including SweatByte.
More free tools
Results are estimates for healthy adults and general information, not medical advice. Talk to a doctor or registered dietitian before big changes to your diet, especially if you have a health condition, take medicines or are pregnant.