One Rep Max Calculator
Enter a weight and the reps you completed to estimate your one rep max.
| Percent | Weight |
|---|---|
| 100% | 229 lb |
| 95% | 218 lb |
| 90% | 206 lb |
| 85% | 195 lb |
| 80% | 183 lb |
| 75% | 172 lb |
| 70% | 160 lb |
The Epley and Brzycki formulas
Epley multiplies the weight by one plus reps over 30. Brzycki uses weight times 36 over 37 minus reps. They agree closely in the low-rep range and drift apart as reps climb, so this calculator averages them for a steadier number.
How to test it well
Pick a set you took close to failure, ideally between three and six reps, and leave a clean rep in the tank. Estimates from high-rep sets run long, and a set you stopped short runs short. Use the same lift and range of motion you want to predict.
Using the number
Treat the estimate as a training tool, not a max you must attempt. Work off percentages of it for volume and intensity, and retest every few weeks. Never round up and chase a number on a cold day.
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Questions about this calculator
How do I calculate my one rep max?
Use Epley: weight times one plus reps divided by 30, or Brzycki: weight times 36 over 37 minus reps. Averaging the two gives a steady estimate.
How accurate is a 1RM calculator?
It is most accurate for sets of three to six reps taken near failure, usually within a few percent. Estimates from high-rep or easy sets run less reliable.
Should I actually test my one rep max?
You do not have to. Use the estimate for training loads and only test a true max if you are prepared, warmed up, and spotting safely.
What is a good one rep max for my bodyweight?
It varies by lift, training age, and bodyweight. Compare your lifts to your own past numbers rather than to other people.
How often should I retest?
Every four to eight weeks is plenty. Retest with the same lift and rep range so the numbers are comparable.
Why do the two formulas disagree?
Each formula models fatigue differently, so they match closely at low reps and diverge as reps rise. The averaged value splits the difference.