One Rep Max (1RM) Calculator
Estimate your theoretical maximum on any exercise using the Epley formula. Enter the weight lifted and repetitions performed to get your estimated 1RM.
How does the calculation work?
The theoretical one-rep maximum (1RM) is the maximum load you can lift for a single repetition with proper form. Testing it directly is demanding and risky, especially without a spotter. For this reason, predictive formulas based on submaximal performance are widely used.
The Epley formula (1985) is one of the most reliable and commonly used formulas in strength sports:
For example, if you lift 100 kg for 5 reps: 1RM = 100 × (1 + 5/30) = 100 × 1.167 = ~117 kg.
The accuracy of the formula is optimal with repetitions between 1 and 10. Beyond 10 repetitions, the estimate becomes less reliable because muscular endurance factors begin to play a larger role than absolute maximal strength.
Load Percentage Table
Once your 1RM is calculated, use this table to determine the training load based on your workout objective.
| % of 1RM | Estimated max reps | Objective |
|---|---|---|
| 100% | 1 reps | Maximal single |
| 95% | 2 reps | Very heavy |
| 90% | 3 reps | Heavy |
| 85% | 5 reps | Heavy |
| 80% | 6 reps | Moderate-heavy |
| 75% | 8 reps | Moderate |
| 70% | 10 reps | Moderate |
| 65% | 12 reps | Light-moderate |
| 60% | 15 reps | Light |
When to use 1RM in training?
Maximal Strength
Use loads at 85-95% of 1RM for 1-5 reps. Long rest periods (3-5 minutes). Ideal for powerlifting and strength sports.
Hypertrophy
Use loads at 65-80% of 1RM for 6-12 reps. Moderate rest (60-120 sec). Maximizes muscle growth.
Muscular Endurance
Use loads at 50-65% of 1RM for 12-20+ reps. Short rest (30-60 sec). Improves endurance.
Power
Use loads at 40-70% of 1RM with explosive execution (box jumps, cleans). Focus on speed, not absolute weight.
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Track your 1RM over time with TrainDojo
With TrainDojo you log every session, monitor progressive overload, and see your estimated 1RM grow over time thanks to your complete workout history.