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About This Calculator
Your one-rep max is the heaviest weight you can lift for a single repetition of a given exercise with proper form. This calculator estimates your 1RM using the weight and repetitions from a recent set, applying formulas like Epley, Brzycki, or Lombardi. Knowing your 1RM allows you to program training percentages accurately without the injury risk of actually testing a true maximum lift.
Quick Tips
- 1 Never test a true 1RM without a spotter or safety pins.
- 2 Estimates are most accurate when based on sets of 3-5 reps.
- 3 Your 1RM can vary 10%+ depending on sleep, stress, and nutrition.
Example Calculation
A lifter bench presses 185 lbs for 8 reps (Epley formula).
1RM estimate: 228 lbs | 90% (heavy): 205 lbs | 80% (strength): 182 lbs | 70% (hypertrophy): 160 lbs
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.