How it’s worked out
Two widely used formulas turn a set of several reps into an estimated single-rep maximum. The calculator shows both and their average:
Epley (1985): 1RM = weight × (1 + reps ÷ 30) Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps)
They agree at 10 reps and drift apart above it, so a set of 10 or fewer gives the best estimate.
Worked example
100 kg for 5 reps: Epley gives 116.7 kg and Brzycki 112.5 kg, an average of 114.6 kg. 80 kg for 10: both give 106.7 kg, because the two formulas agree exactly at 10 reps.
| Of 1RM | Weight | About this many reps |
|---|---|---|
| 100% | 114.6 kg | 1 |
| 95% | 108.9 kg | 2 |
| 90% | 103.1 kg | 3 |
| 85% | 97.4 kg | 5 |
| 80% | 91.7 kg | 8 |
| 75% | 85.9 kg | 10 |
| 70% | 80.2 kg | 13 |
| 60% | 68.8 kg | 20 |
| 50% | 57.3 kg | 30 |
The reps come from Epley’s formula turned round; people differ, so treat them as a starting point.
How to read the result
- Estimated one rep max: the average of the two formulas.
- Percentages: the weights for programmes written as a share of 1RM, with each rounded to the nearest 2.5 kg or 5 lb you can load.
Common mistakes
- Using a set of 15 or more reps: the estimate gets less reliable.
- Counting reps with poor form: only clean reps count.
- Treating the estimate as a weight to attempt: it’s for planning training, not a target to test.
How to use it
- Type the weight you lifted, in kg or lb.
- Type how many clean reps you managed.
- Use the percentage chart to plan your working sets.
Questions
How do I calculate my one rep max?
Do a hard set of 10 reps or fewer, then use a formula such as Epley’s: weight × (1 + reps ÷ 30). 100 kg for 5 reps is about 116.7 kg.
Which 1RM formula is most accurate?
None is best for everyone; Epley and Brzycki are the most used and agree closely up to about 10 reps, which is why the calculator shows both and their average.
What is 80% of my one rep max for?
Programmes often prescribe sets by percentage: around 80% is roughly 8 reps for most people, a common strength range.
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Elsewhere on Yuzool
- Progressive overload: how to add weight Lift Log’s guide
- Lift Log to log your sets and PRs
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