One Rep Max Calculator
One rep max (1RM) is the maximum weight you can lift for a single repetition of an exercise. It is the standard measure of absolute strength and the foundation of percentage-based strength programming.
How to Use
Enter the weight you lifted and the number of reps you completed. The calculator estimates your 1RM using your chosen formula. For best accuracy, use a set of 1–10 reps taken close to failure.
Formulas
Epley (Default)
The most commonly referenced formula, developed in 1985.
1RM = weight × (1 + reps / 30)
Brzycki
A slightly more conservative estimate, accurate up to about 10 reps.
1RM = weight × (36 / (37 − reps))
Lombardi
Uses an exponential model, tends to produce higher estimates at higher rep ranges.
1RM = weight × reps^0.1
Training Percentages
Once you know your 1RM, use these general guidelines for programming:
| % of 1RM | Reps per Set | Training Goal |
|---|---|---|
| 90–100% | 1–3 | Maximal strength |
| 80–90% | 3–5 | Strength |
| 70–80% | 6–12 | Hypertrophy |
| 60–70% | 12–20 | Muscular endurance |
Limitations
All 1RM estimation formulas assume a consistent strength-to-endurance ratio, which varies between individuals. Highly trained athletes and those who excel at higher rep ranges may find estimates less accurate. Always approach near-maximal lifts with proper warm-up and a spotter.