Calculator
One-rep max calculator
Your one-rep max (1RM) is the most weight you can lift for a single rep. Enter a weight and the reps you hit with it, and this calculator estimates your 1RM with the Epley and Brzycki formulas, then builds a percentage table for programming your loads.
Enter a hard set — weight and reps.
Units
Result
Worked example
Squat 100 kg for 5 reps: Epley estimates 100 × (1 + 5/30) ≈ 116.5 kg, Brzycki estimates 100 × 36 / (37 − 5) = 112.5 kg — an average 1RM of about 114.5 kg. Training at 80% (≈91.5 kg) then puts you in a solid 5-rep working range.
Frequently asked questions
- How accurate is a 1RM calculator?
- Estimates from a set of 1–5 reps are usually within a few percent of a true max. Accuracy drops as reps rise, because fatigue and rep efficiency vary more between lifters past ~10 reps.
- Should I use the Epley or Brzycki formula?
- Both are well established and close in the 1–10 rep range. Epley tends to estimate slightly higher at high reps, Brzycki slightly lower. This calculator shows both and an average so you can pick a sensible training number.
- How many reps should I use for the best estimate?
- Use a hard set of 3–6 reps. It is heavy enough to be representative but far enough from a true single to stay safe and repeatable.