Estimating 1RM avoids risky max attempts and helps programme training intensity.
How to use the One-Rep Max Calculator
- Weight lifted
- Reps completed
Results update as you type, and every field accepts the units shown in its menu.
How it works
The weight and reps you can do are entered into each formula; estimates are most accurate for 10 reps or fewer.
Inputs explained
| Field | What to enter |
|---|---|
| Weight lifted | Units: kg, lb, g, oz, st |
| Reps completed | A number |
What each result means
- Estimated 1RM (Brzycki) = [Weight lifted]×36÷(37 – [Reps completed])
- 90% of 1RM = [Estimated 1RM (Epley)]×0.9
- 80% of 1RM = [Estimated 1RM (Epley)]×0.8
- 70% of 1RM = [Estimated 1RM (Epley)]×0.7
Example values
How the main result changes when Weight lifted changes and everything else stays at the example values above:
| Weight lifted (kg) | Estimated 1RM (Epley) (kg) |
|---|---|
| 40 | 48 |
| 60 | 72 |
| 80 | 96 |
| 100 | 120 |
| 120 | 144 |
| 160 | 192 |
Formula
Epley: 1RM = w × (1 + reps ÷ 30)Brzycki: 1RM = w × 36 ÷ (37 − reps)Worked example
Inputs — Weight lifted: 80 kg; Reps completed: 6.
Results — Estimated 1RM (Epley) = 96 kg; Estimated 1RM (Brzycki) = 92.9 kg; 90% of 1RM = 86.4 kg; 80% of 1RM = 76.8 kg; 70% of 1RM = 67.2 kg.
Frequently asked questions
Which formula is best?
They agree closely at low reps; at high reps all become less accurate.
Should beginners test a true 1RM?
It is safer to estimate from sets of 3–8 reps.
What formula does the One-Rep Max Calculator use?
Epley: 1RM = w × (1 + reps ÷ 30).