One-Rep Max (1RM) Strength Calculator
Calculate your one-rep max (1RM) based on the weight you lifted and the number of repetitions completed.
What is an One-Rep Max?
Your one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. It is the gold standard for measuring absolute strength in powerlifting and weightlifting.
Why Estimate It?
Testing your true 1RM is incredibly taxing on your central nervous system and carries a high risk of injury if form breaks down. Estimating your 1RM using a sub-maximal load (like your 5-rep max) is far safer and still highly accurate for programming your training cycles.
The Estimation Formulas
Because humans vary in their ratio of fast-twitch to slow-twitch muscle fibers, no single formula is perfect. This calculator uses an average of the three most popular formulas:
- Epley: Weight * (1 + Reps/30)
- Brzycki: Weight * (36 / (37 - Reps))
- Lombardi: Weight * Reps^0.10
Frequently Asked Questions
Is the calculation accurate for high reps?
No. 1RM estimations become highly inaccurate if you use a set with more than 10 repetitions. For the most accurate estimate, use a heavy set of 3 to 5 reps.
Disclaimer: This calculator is for educational and informational purposes only. It is not a medical diagnosis or professional medical advice. The results provided should not be relied upon as a substitute for professional medical evaluation. Individual health needs vary greatly based on age, medical history, lifestyle, and other factors. Consult a qualified healthcare provider, doctor, or registered dietitian before making any health or medical decisions. If you are experiencing health concerns, seek immediate medical attention.