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 programming—allowing you to calculate working weights as a percentage of your max.
The Epley Formula (Most Common)
1RM = Weight × (1 + Reps / 30)
Example: You bench press 185 lbs for 8 reps. 1RM = 185 × (1 + 8/30) = 185 × 1.267 = 234 lbs
The Brzycki Formula
1RM = Weight × 36 / (37 − Reps)
More accurate for low rep ranges (under 10): 1RM = 185 × 36 / (37 − 8) = 185 × 36/29 = 229 lbs
The Lombardi Formula
1RM = Weight × Reps^0.10
Comparing Formula Results
| Formula | 185 lbs × 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 |
|---|---|---|
| 50–60% | 15–20 | Muscular endurance |
| 65–75% | 8–12 | Hypertrophy (size) |
| 75–85% | 4–6 | Strength |
| 85–95% | 2–3 | Max strength |
| 95–100% | 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 3–5 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.