How to Calculate Your One Rep Max (1RM)
Your one-rep max (1RM) is the maximum weight you can lift for exactly one repetition with good form. It's the foundation of percentage-based strength training programmingβallowing you to calculate working weights as a percentage of your max.
The Epley Formula (Most Common)
1RM = Weight Γ (1 + Reps / 30)
Example: You bench press 185 lbs for 8 reps. 1RM = 185 Γ (1 + 8/30) = 185 Γ 1.267 = 234 lbs
The Brzycki Formula
1RM = Weight Γ 36 / (37 β Reps)
More accurate for low rep ranges (under 10): 1RM = 185 Γ 36 / (37 β 8) = 185 Γ 36/29 = 229 lbs
The Lombardi Formula
1RM = Weight Γ Reps^0.10
Comparing Formula Results
| Formula | 185 lbs Γ 8 reps |
|---|---|
| Epley | 234 lbs |
| Brzycki | 229 lbs |
| Lombardi | 231 lbs |
| Average | 231 lbs |
Using an average of multiple formulas gives a more reliable estimate.
Using 1RM for Training Percentages
| % of 1RM | Target Reps | Training Goal |
|---|---|---|
| 50β60% | 15β20 | Muscular endurance |
| 65β75% | 8β12 | Hypertrophy (size) |
| 75β85% | 4β6 | Strength |
| 85β95% | 2β3 | Max strength |
| 95β100% | 1 | Testing max |
Important Safety Note
Formula-based 1RMs are estimates. Predicting from sets of 8 or more reps is less accurate than sets of 3β5 reps. For safety, test your actual 1RM only after a thorough warmup with proper form practice.
Use our 1RM calculator to find your max from any working weight.