One Rep Max Calculator

Your 1RM is the maximum weight you can lift for a single repetition with proper form. It is used to set training intensity percentages for strength programs. Testing your true 1RM carries injury risk, so estimating from submaximal lifts is safer.

Most accurate for 1–5 rep sets (within 2–5%). Accuracy decreases for higher rep sets (10+) because the relationship between reps and maximal strength varies by individual, muscle fiber type, and exercise type. Experienced lifters can often handle a higher percentage of their 1RM for multiple reps than beginners.

1RM = 100% | 3 reps ≈ 93% | 5 reps ≈ 87% | 8 reps ≈ 80% | 10 reps ≈ 75% | 12 reps ≈ 70% | 15 reps ≈ 65%. These are guidelines — individual responses vary significantly.

Not regularly. True 1RM testing is taxing and carries higher injury risk. Most strength programs use percentage-based training from an estimated or tested 1RM. Test your true 1RM only at the end of training cycles or for competition, with a spotter.

Neither is universally best. Both are validated formulas that perform similarly for 1–6 rep ranges. Brzycki tends to be more accurate at lower rep counts; Epley can overestimate at very high reps. Averaging both (as this calculator does) improves overall accuracy.