One rep max calculator
Estimate the most you could lift once from a lighter set.
Estimated 1RM (average)
Rounded for displayEstimated 1RM (average): ≈ 114.6
- Epley
- ≈ 116.7
- Brzycki
- 112.5
- 90% of 1RM
- ≈ 103.1
- 80% of 1RM
- ≈ 91.7
- 70% of 1RM
- ≈ 80.2
How it works
A one-repetition maximum (1RM) is the heaviest weight you can lift once with good form. It can be estimated from a heavier set of a few reps instead of testing it directly.
The Epley formula (1985) and the Brzycki formula (1993) are the most widely used. They agree closely at around 10 reps and differ more at low and high counts; the average of the two is shown first. A single rep returns the weight itself.
Warm up properly and use a spotter for heavy lifts. This is a general estimate, not medical advice. For personal guidance, speak to a doctor or registered dietitian.
Formula
Epley: 1RM = weight × (1 + reps ÷ 30) Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Worked example
Lifting 100 kg for 5 reps: Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg and Brzycki 100 × 36 ÷ 32 = 112.5 kg, an average of 114.6 kg. 80% of that is 91.7 kg.
Questions people ask
How many reps should I use?
Sets of 2 to 10 reps give the most reliable estimates. Above 10, endurance starts to affect the result.
Why do Epley and Brzycki give different answers?
They were fitted to different data. They match at 10 reps and drift apart above and below.