One Rep Max Calculator

For sets of 1-5 reps, these formulas are highly accurate, typically within 5% of actual 1RM. Accuracy decreases as rep count increases: at 10 reps, the error is typically 8-12%. At 15+ reps, the estimate can be off by 15% or more because muscular endurance plays an increasingly large role relative to pure strength. For programming purposes, use calculated 1RM from a set of 3-8 reps for the best accuracy.

Training intensity depends on your goal. For maximum strength (1-3 reps), train at 90-100% of 1RM. For strength and hypertrophy (4-6 reps), use 80-90%. For hypertrophy (6-12 reps), 65-80% is the standard recommendation. For muscular endurance (12+ reps), use below 65%. Many advanced programs periodize across these ranges, spending weeks at different percentages to develop multiple strength qualities simultaneously.

Testing actual 1RM is appropriate for experienced lifters who have solid technique and a training partner or spotter. For beginners and intermediate lifters, calculating 1RM from a submaximal set is safer and nearly as accurate. True 1RM testing places significant stress on the nervous system and joints, and the risk of injury outweighs the marginal accuracy gain for most people. Recalculate from a heavy working set every 4-8 weeks as a safer alternative.

No. Your 1RM is exercise-specific. A 315 lb squat 1RM tells you nothing about your deadlift or bench press. Each major lift should be calculated independently. Even the rep-to-max relationship can differ between exercises: some people perform better relative to their 1RM on multi-joint compound lifts versus isolation exercises. Always use the specific exercise data when calculating percentages for a given movement.