One Rep Max (1RM) Calculator
Estimate your one-rep max from the weight and reps you lifted.
Uses the Epley formula to calculate your maximum strength for any exercise.
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Estimated 1RM
One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form.
Epley Formula (most widely used):
1RM = Weight × (1 + Reps / 30)
Other common formulas:
- Brzycki:
1RM = Weight × (36 / (37 - Reps)) - Lander:
1RM = Weight × 100 / (101.3 - 2.67123 × Reps)
Training percentages from 1RM:
| % of 1RM | Estimated Reps | Training Goal |
|---|---|---|
| 100% | 1 rep | Max strength test |
| 90% | ~3–4 reps | Strength |
| 80% | ~7–8 reps | Hypertrophy |
| 70% | ~10–12 reps | Muscular endurance |
| 60% | ~15–17 reps | Endurance |
| 50% | ~20+ reps | Warm-up / rehab |
Important notes:
- The formula is most accurate with 1–10 reps
- Accuracy decreases above 10 reps
- Results are estimates — actual 1RM may vary based on technique, fatigue, and experience
- Always use a spotter when testing actual 1RM
Works in both metric (kg) and imperial (lbs) — enter whichever you use.