1RM calculator
Enter a weight and reps you completed. We estimate your one-rep max with Epley as the primary formula and Brzycki as a second opinion, then map working-set loads from 50% to 95%.
How it works
- Lift a challenging set of 1–36 reps and note the load.
- We compute Epley and Brzycki estimated 1RMs.
- Use the percentage table to pick warm-up and working-set weights.
Epley (primary)
117 kg
Brzycki (secondary)
113 kg
| % of 1RM | Epley | Brzycki |
|---|---|---|
| 50% | 58.3 | 56.3 |
| 55% | 64.2 | 61.9 |
| 60% | 70.0 | 67.5 |
| 65% | 75.8 | 73.1 |
| 70% | 81.7 | 78.8 |
| 75% | 87.5 | 84.4 |
| 80% | 93.3 | 90.0 |
| 85% | 99.2 | 95.6 |
| 90% | 105 | 101 |
| 95% | 111 | 107 |
Questions
- What is the Epley 1RM formula?
- Epley estimates one-rep max as weight × (1 + reps ÷ 30). It is widely used for moderate rep sets.
- What is the Brzycki formula?
- Brzycki estimates 1RM as weight × 36 ÷ (37 − reps). We show it as a secondary check next to Epley.
- How accurate is a calculated 1RM?
- Formulas are estimates. Accuracy drops as reps climb above ~10. Treat results as planning aids, not guarantees.
- How do I use the percentage table?
- Pick a target % of 1RM for your working sets (for example 70–85% for hypertrophy or strength work) and load the matching weight from the table.
OptaFit tools provide general estimates only. They are not medical, dietary, or fitness advice. Talk to a qualified professional before changing your diet or training.