🏋️ One Rep Max Calculator
Testing a true one-rep max is hard and risky. Instead, lift a weight for several clean reps and estimate your 1RM from it.
Estimated 1RM
How the One Rep Max Calculator works
Two well-known formulas are shown — Epley and Brzycki — plus their average. Estimates are most accurate between about 2 and 10 reps.
Epley: 1RM = Weight × (1 + Reps ÷ 30)
Brzycki: 1RM = Weight × 36 ÷ (37 − Reps)
Step-by-step calculation
- 1Lift a weight for as many clean reps as you can (2–10 is best).
- 2Enter the weight and reps.
- 3Apply the Epley and Brzycki formulas.
- 4Use the average as your estimate.
Worked example
100 kg for 5 reps: Epley = 100 × (1 + 5/30) = 116.7 kg, Brzycki = 100 × 36 ÷ 32 = 112.5 kg, average about 114.6 kg.
One Rep Max Calculator examples
| Weight lifted (kg or lb) | Estimated 1RM |
|---|---|
| 50 | 57.3 |
| 75 | 85.9 |
| 100 | 114.6 |
| 125 | 143.2 |
| 150 | 171.9 |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a One Rep Max Calculator?
Plan strength training without risky max attempts.
Important factors that can affect your results
- Fatigue and warm-up.
- Exercise type (formulas fit big lifts best).
- Accuracy drops above 10 reps.
Frequently asked questions
Kilograms or pounds?
Either. The result uses the same unit you enter.
Should I try my real 1RM?
Only with good technique, a warm-up and a spotter. Many people never need to test it directly.
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Last reviewed November 2026 · How we build and check our tools · Report a problem