One Rep Max Calculator
Estimate your one rep maximum (1RM) for any lift using popular formulas. Calculate training percentages for different rep ranges.
Estimated 1RM (Epley formula)
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Training percentages
What is One Rep Max Calculator?
Your one rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise with proper form. It is the standard benchmark for measuring strength in powerlifting and resistance training. Because attempting a true 1RM can be risky, this calculator estimates it from a submaximal set using proven formulas.
How to use
- 1 Enter the weight you lifted in your working set.
- 2 Select kilograms or pounds depending on your equipment.
- 3 Enter the number of reps you completed with that weight.
- 4 The calculator returns your estimated 1RM using the Epley, Brzycki, and Lander formulas.
- 5 Use the training percentages table to plan your programming at 50% to 100% of your estimated max.
Formula
Example calculation
If you lifted 80 kg for 8 reps, the Epley formula gives 80 x (1 + 8/30) = 101.3 kg. The Brzycki formula gives 80 x 36 / (37 - 8) = 99.3 kg. The average across all three formulas would be your most reliable estimate.
Frequently asked questions
Which formula is most accurate?
No single formula is universally best. The Epley and Brzycki formulas tend to be most accurate for sets of 3 to 10 reps. Accuracy drops significantly above 10 reps because fatigue plays a larger role.
What rep range gives the best estimate?
Sets of 3 to 6 reps typically yield the most accurate 1RM predictions. Sets over 10 reps introduce more error because they test muscular endurance as much as strength.
Should I ever attempt an actual 1RM?
Only with proper warm-up, a spotter, and solid technique. Beginners should rely on estimated 1RM values rather than testing their true max, as the risk of injury outweighs the benefit for most training goals.
How do I use 1RM for programming?
Most strength programs prescribe work sets as a percentage of 1RM. Hypertrophy work typically falls in the 65-80% range for 6-12 reps, while strength work sits at 80-95% for 1-5 reps.
How often does my 1RM change?
Your estimated 1RM can increase within weeks of consistent training, especially for beginners. Recalculate every 4 to 8 weeks as you progress to keep your training percentages accurate.