One Rep Max Calculator
Estimate one-rep max strength from weight lifted and repetitions.
How this calculator works
How to use this calculator
Enter the weight lifted and the number of repetitions completed. The calculator estimates your one-rep max.
Formula used
This calculator averages common Epley and Brzycki estimates when possible. Epley formula: 1RM = Weight × (1 + Reps ÷ 30). Brzycki formula: 1RM = Weight × 36 ÷ (37 − Reps).
Example calculation
If you lift 100 for 5 reps, the estimated one-rep max is about 114.2.
What the result means
The estimated 1RM is an approximate maximum weight you might lift for one repetition. Real performance depends on technique, fatigue, exercise type, and safety.
Frequently asked questions
Is this exact?
No. It is an estimate based on repetition performance.
Should beginners test one-rep max?
Beginners should be cautious and prioritize safe technique. Consider working with a qualified coach.
What units should I use?
Use any weight unit, such as kg or lb. The result will be in the same unit.