1RM Epley
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Epley 1RM Calculator estimates your one-rep maximum (1RM) based on the weight used in an exercise set and the number of repetitions performed. It's ideal for athletes who want to assess strength without risking injuries by lifting near-maximal loads. The formula is straightforward: 1RM = weight × (1 + repetitions/30).
The calculation assumes weight increases proportionally with repetitions, adjusting the estimate as muscle fatigue occurs. For example, if you lifted 80kg for 8 reps, your estimated 1RM would be 80 × (1 + 8/30) = 97.6kg. It's crucial to perform the set with proper technique and consistent pace for accurate results.
Use this calculator after a controlled set of strength training with a known weight and counted repetitions. It's especially useful for planning hypertrophy or strength programs by adjusting loads without overexertion. Avoid using it for complex movements or unstable equipment, where biomechanics significantly affect outcomes.
Remember that the calculated 1RM is an approximation and may vary based on factors like recovery, motivation, and technical form. For greater accuracy, consult a fitness professional or use supervised progressive testing methods.
Frequently asked questions
Do I need to perform a maximal lift to use the calculator?
No. The formula estimates 1RM based on a set with known weight and repetitions, eliminating the need to lift near-maximal loads directly.
What is the error margin of the calculation?
Accuracy varies, but studies suggest up to 5-10% error compared to direct tests, depending on technique consistency and weight used.
Can I use this for sets with more than 10 repetitions?
The formula works best for 1-10 reps. For sets above 12 reps, consider formulas like Brzycki for better accuracy.
Is it safe to calculate my 1RM without supervision?
Yes, if using appropriate weights and avoiding overexertion. If testing directly, always have a partner or professional present for safety.
Why does the formula use 30 as the divisor?
The number 30 comes from studies analyzing strength-fatigue relationships, proportionally adjusting weight increase with repetitions.