One-rep max (1RM) calculator
Estimate your one-rep max (1RM) and the loads to train at different intensities.
Epley formula. Estimate — do not attempt a true 1RM without supervision and warm-up.
How the calculation works
1RM is the max load you could lift once. The Epley formula estimates: 1RM = weight × (1 + reps ÷ 30). The percentages help plan training.
Examples
- 80 kg for 5 reps: 1RM ≈ 80 × (1 + 5/30) = 93 kg.
- With a 100 kg 1RM, hypertrophy training (75%): 75 kg.
Frequently asked questions
How many reps to use?
The estimate is more accurate with up to ~10 reps.
Is it safe to test a true 1RM?
Only with good form, warm-up and ideally a spotter. For most people, the rep-based estimate is safer.
Why know your 1RM?
To program training by percentages (strength, hypertrophy, endurance) and track strength progress.
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Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources