Find your maximum strength using proven scientific formulas.
| Formula | 1RM | vs Epley |
|---|
Enter the weight you lifted and the number of reps you completed. Optionally, select your exercise and enter your bodyweight to see your strength level relative to your body size. Hit Calculate 1RM and get your estimated one rep max plus a full percentage breakdown table.
Your one rep max (1RM) is the gold standard for measuring strength. But testing a true 1RM carries injury risk โ most lifters shouldn't walk up to a bar cold and try to max out. That's where estimation comes in. If you can bench press 185 lbs for 8 reps, this calculator can estimate your 1RM at roughly 235โ240 lbs without you ever having to attempt that single heavy lift.
Coaches and athletes use 1RM estimates to program training percentages. A powerlifter working at 80% 1RM for sets of 5 needs to know what that 80% actually is. A beginner trying to add muscle might work at 65โ75% of 1RM for higher rep sets. Without a 1RM reference point, it's hard to structure progressive overload โ the foundation of any strength program.
The sweet spot for accuracy is 3โ10 reps. A set of 5 at a challenging weight gives a very reliable 1RM estimate. The further you go above 10 reps, the less accurate these formulas become, because muscle endurance starts playing a larger role than pure strength.
Several peer-reviewed formulas exist, each with slightly different weighting. This tool calculates all of them and defaults to the Epley formula (widely considered most accurate for most lifters):
The percentage breakdown table shows training loads from 50% to 100% of your estimated 1RM โ the standard reference used by coaches worldwide.
For sets of 3โ8 reps with proper effort, these formulas are typically accurate within 5โ10%. The more reps you perform, the less accurate the estimate becomes. A 3-rep set will give you a better 1RM estimate than a 15-rep set.
The Epley formula is the most commonly used and works well for most people across a wide rep range (3โ12 reps). Brzycki is preferred for low-rep heavy sets (1โ5 reps). When in doubt, look at the average across all formulas โ it's often more reliable than any single one.
Yes โ the math applies to any barbell, dumbbell, or machine exercise. However, 1RM estimates are most commonly used for compound lifts: squat, bench press, deadlift, and overhead press. Isolation exercises like curls are less commonly tracked this way.
The strength level compares your 1RM to your bodyweight using standard ratios. For example, a 1.5ร bodyweight bench press is considered Advanced for most populations. These standards are generalizations โ they vary by sex, age, training history, and body composition.