One-rep max calculator
Estimate your one-rep max (1RM) from a weight and a number of reps.
- Instant
- Free
- Private (processed locally)
- No sign-up
Estimate your max strength safely
Enter a weight and a number of reps: the tool computes your 1RM with the Epley and Brzycki formulas, their average, and a table of loads by percentage.
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Enter the weight
The load of your set.
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Enter the reps
Ideally between 3 and 10.
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Read 1RM and %
To plan strength and hypertrophy.
Example: 100 kg × 5 reps
| Method | Result |
|---|---|
| Epley | 116.7 kg |
| Brzycki | 112.5 kg |
| Average (1RM) | 114.6 kg |
| 90% of 1RM | ≈ 103.1 kg |
| 80% of 1RM | ≈ 91.7 kg |
Indicative estimate, not a medical program. Warm up and progress carefully toward heavy loads.
Frequently asked questions
What is 1RM?
The 1RM (one-rep max) is the maximum load you can lift once on an exercise. It is estimated safely from a sub-maximal set: the weight lifted and the number of repetitions.
Which formulas are used?
Epley: 1RM = weight × (1 + reps/30). Brzycki: 1RM = weight × 36 / (37 − reps). With 100 kg × 5 reps, you get 116.7 kg (Epley) and 112.5 kg (Brzycki), i.e. an average of 114.6 kg.
Why stay under 12 reps?
The formulas are reliable on short sets (1 to 10-12 reps). Beyond that, fatigue and technique distort the estimate and the gap between formulas grows. For an accurate 1RM, test on 3 to 6 reps.
What is the percentage table for?
To plan your sessions: strength is often trained at 85-95% of 1RM (1-5 reps), hypertrophy at 67-80% (8-12 reps). The table converts your estimated 1RM into concrete loads by percentage.