One Rep Max (1RM) Calculator
Calculate your estimated one-rep max (1RM) for any lift using the Epley formula. Enter weight and reps performed.
Understanding 1RM
Your One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. Our calculator uses the Epley formula: 1RM = Weight × (1 + Reps/30). This is considered one of the most accurate prediction formulas.
Knowing your 1RM helps you program training at the right intensity. Common training zones: Strength (85-100% 1RM), Hypertrophy (65-85%), Endurance (50-65%).
Training Percentages
- 90-100% 1RM: 1-3 reps — maximal strength
- 80-90% 1RM: 3-5 reps — strength
- 70-80% 1RM: 6-10 reps — hypertrophy (muscle growth)
- 60-70% 1RM: 12-15 reps — muscular endurance
- 50-60% 1RM: 15+ reps — endurance/warm-up
Frequently Asked Questions
How accurate is the Epley formula?
The Epley formula is most accurate for sets of 2-10 reps. Beyond 10 reps, accuracy decreases. For the best estimate, use a weight you can lift for 3-5 reps.
Should I test my actual 1RM?
Testing actual 1RM carries injury risk, especially for beginners. Using a submaximal estimate (like this calculator) is safer and nearly as accurate for programming purposes.
How often should I update my 1RM?
Reassess every 4-8 weeks as you progress. Beginners may see rapid increases, while advanced lifters may only improve every few months.