One Rep Max Calculator
0 lbs estimated one-rep max
| % of 1RM | Weight | Typical Rep Range |
|---|---|---|
| 100% | 1 rep | |
| 95% | 2 reps | |
| 90% | 4 reps | |
| 85% | 6 reps | |
| 80% | 8 reps | |
| 75% | 10 reps | |
| 70% | 12 reps | |
| 65% | 15 reps |
How the Estimate Is Calculated
This calculator averages two widely used prediction equations. The Epley formula estimates one-rep max as weight × (1 + reps ÷ 30), while the Brzycki formula uses weight × 36 ÷ (37 − reps). Both are well-established in strength-training literature and tend to agree closely within the 2-10 rep range; they diverge more at higher rep counts, which is why estimates get less reliable above roughly 10-12 reps. The headline figure above is the average of the two.
Why It's an Estimate, Not a Guarantee
One-rep max formulas assume a fairly typical strength-endurance ratio and consistent bar speed and technique across the set. Fatigue, bar path efficiency, and how close the set was taken to failure all affect real-world accuracy, so treat the result as a solid planning number rather than a guaranteed lift. If you want a training weight for a specific rep target, use the percentage table above rather than testing a true 1RM directly, which carries a higher injury risk without a spotter or coach present.
Putting Your Max to Use
Once you have an estimated max, the percentage breakdown helps structure hypertrophy, strength, or power blocks without needing to retest every few weeks. Pair this with a protein calculator to support recovery, and a lean body mass calculator to track body composition changes as your strength progresses. This tool is for training-planning purposes only and isn't a substitute for guidance from a qualified coach or physician, especially if you're returning from injury.
Frequently Asked Questions
Which formula is more accurate, Epley or Brzycki?
Both are close within the 2-10 rep range, which is where most people test. Epley tends to run slightly higher at higher rep counts, while Brzycki tends to run slightly lower and becomes unreliable above about 10 reps because its denominator (37 minus reps) approaches zero. This calculator averages the two for a balanced estimate.
How many reps should I use to estimate my one-rep max safely?
Using a set of 3 to 8 reps taken close to failure gives the most reliable estimate while avoiding the injury risk of testing a true single-rep max without a spotter. Estimates from sets of 12 or more reps are less precise since the formulas assume a fairly standard strength-endurance relationship.