One rep max formulas are most accurate with 1-10 reps. The Epley, Brzycki, and Lander formulas typically agree within 2-5% for low rep ranges. Above 10 reps, accuracy decreases because muscular endurance becomes a larger factor. For best results, use a weight you can lift for 3-5 reps with good form.
- 1-5 reps: highest accuracy (±2-3% of actual 1RM)
- 6-10 reps: good accuracy (±5% of actual 1RM)
- 11-15 reps: moderate accuracy (±8-10%)
- 15+ reps: poor accuracy (endurance dominates)
- Epley tends to overestimate at higher rep ranges
- Brzycki tends to be more conservative
| Formula | Best For | Tendency | Accuracy (1-5 reps) |
|---|---|---|---|
| Epley | All rep ranges | Slightly high at 10+ reps | ±2-3% |
| Brzycki | 1-10 reps | Conservative estimate | ±2-3% |
| Lander | 1-10 reps | Middle ground | ±2-4% |
| Average of 3 | General use | Best overall estimate | ±2% |
