One Rep Max (1RM) Calculator
Calculate your one rep max for weightlifting
Calculator
Enter the weight and number of reps you performed. Works best with 1-10 reps.
How to Use
Calculate your one rep max for any lift
Enter weight lifted
Input the weight you used
Enter reps completed
Input the number of reps performed
View 1RM estimate
See your estimated one rep max
See training zones
View percentages for different training goals
1RM Formulas
Epley: 1RM = weight × (1 + reps/30) Brzycki: 1RM = weight × 36 / (37 - reps)
Most accurate with 1-5 reps. Results are estimates - actual 1RM may vary 5-10%.
Frequently Asked Questions
1RM is the maximum weight you can lift for one repetition with proper form. It's used to measure strength progress and calculate training loads. Knowing your 1RM helps program percentages (e.g., 70% of 1RM for 8 reps).
Use a submaximal formula. Most accurate with 3-5 reps. Example (Epley formula): 1RM = weight × (1 + reps/30). If you lift 200 lbs for 5 reps: 1RM = 200 × (1 + 5/30) = 233 lbs. Accuracy decreases with higher reps (10+).
Epley, Brzycki, and Lander formulas are most common. They agree within 5% for low rep ranges. Epley tends to estimate slightly higher. Use the same formula consistently to track progress. Best accuracy comes from 3-5 rep tests.
Every 8-12 weeks for experienced lifters. Beginners should wait 3-6 months before testing true 1RM. Use submaximal estimation for regular tracking. Always warm up thoroughly and have a spotter for safety.