One Rep Max Calculator
Estimate your one-rep max (1RM) from a lifted weight and rep count using the Epley and Brzycki formulas.
- 1RM (Brzycki)
- 112.5 kg
- 90% training load
- 105 kg
- 80% training load
- 93.3 kg
Formula: 1RM = w × (1 + reps ÷ 30) (Epley) | 1RM = w × 36 ÷ (37 − reps) (Brzycki)
About One Rep Max Calculator
One Rep Max Calculator is a free online calculator that gives you an instant, accurate result as you type. Estimate your one-rep max (1RM) from a lifted weight and rep count using the Epley and Brzycki formulas.
The calculation uses the standard formula 1RM = w × (1 + reps ÷ 30) (Epley) | 1RM = w × 36 ÷ (37 − reps) (Brzycki) and updates live with every change to the inputs. Everything runs client-side in your browser — fast, private, and free to use as often as you like.
1RM formulas are most accurate for sets of 10 reps or fewer; Epley and Brzycki agree exactly at 10 reps and diverge slightly elsewhere.
Results are estimates for educational purposes and not medical advice.
Frequently Asked Questions
Is One Rep Max Calculator free to use?
Yes. One Rep Max Calculator is completely free, with no sign-up, no downloads, and no usage limits. You can use it as many times as you like on any device with a web browser.
How accurate is this calculator?
The calculator applies the standard formula (1RM = w × (1 + reps ÷ 30) (Epley) | 1RM = w × 36 ÷ (37 − reps) (Brzycki)) with full floating-point precision and rounds only the displayed result. For most practical purposes the results are exact.
Which 1RM formula should I trust?
Epley tends to estimate slightly higher for high-rep sets while Brzycki is slightly more conservative; averaging the two is a reasonable practical estimate.
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