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What is One Rep Max?
One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It is the gold standard measure of strength in weightlifting and is used to program training percentages for powerlifting, bodybuilding, and athletic strength programs.
The Three 1RM Formulas
The Brzycki formula is: 1RM = weight × (36 / (37 - reps)). The Epley formula is: 1RM = weight × (1 + reps/30). The Lander formula is: 1RM = (100 × weight) / (101.3 - 2.67123 × reps). Each formula is most accurate with reps below 10. Results tend to converge for low rep ranges.
Training with Percentages of 1RM
Strength programs commonly prescribe weights as percentages of 1RM: 50-65% for endurance, 67-85% for hypertrophy (muscle growth), 85-95% for strength, and 95%+ for peaking. Knowing your 1RM allows precise programming without the risk of actually attempting a maximal lift.
When to Test Your 1RM
Direct 1RM testing should be done infrequently — every 8-12 weeks at most — after a proper warm-up and with a spotter. Estimation from submaximal sets is safer and can be done regularly. Use sets of 3-5 reps for the most accurate estimates, as accuracy decreases above 10 reps.
Frequently Asked Questions
The Brzycki and Epley formulas are considered equally accurate for rep ranges of 1-10. The Lander formula can provide a useful third data point. For reps above 10, all formulas become less reliable. Using the average of all three formulas often gives the best estimate.
Use a weight you can lift for 2-6 reps for the most accurate 1RM estimate. Estimates based on sets of 10+ reps tend to overestimate true 1RM. If you can lift a weight for more than 12 reps, increase the weight and test again with fewer reps.
Attempting a true 1RM carries risk of injury, especially without proper warm-up, a spotter, or experience. Estimation from submaximal lifts is safer and nearly as accurate. If you do attempt a 1RM, warm up thoroughly, use proper form, have a spotter, and do not attempt it when fatigued.
Yes, your 1RM is specific to each exercise. You will have different maxes for squat, bench press, deadlift, overhead press, and every other lift. This calculator can be used for any exercise — just enter the weight and reps for that specific lift.