One-Rep Max Calculator
Calculate your maximum weight for one repetition (1RM).
Tip: Don't test your 1RM directly if you're a beginner — use the calculator with 3–10 reps.
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About this digital tool
The one-rep max (1RM) calculator estimates the heaviest weight you can lift once, without testing it directly. Enter the weight you lift and how many repetitions you do, and get the 1RM according to four well-known formulas: Epley, Brzycki, Lander and O'Conner, plus their average.
The formulas are based on the relationship between load and repetitions. For example, Epley: 1RM = weight × (1 + reps ÷ 30). Above 10 reps the estimate becomes less accurate, so use sets of 3-8 reps. 1RM is used to plan training in percentages, such as 70% or 80% of your max. For safety, lift with good technique and a spotter; if you are a beginner, get guidance from a trainer.
How to use
- Enter the weight lifted.
- Set the number of repetitions (2–12).
- See the estimated 1RM and the percentage table.
Frequently asked questions
Which formula is most accurate?
Epley and Brzycki give very similar results for 3–10 reps. Above 10 reps, accuracy drops — use heavier loads.
How is 1RM calculated with the Epley formula?
Epley: 1RM = weight × (1 + reps ÷ 30). For example, 80 kg for 5 reps gives 80 × (1 + 5 ÷ 30) = 93.3 kg.
At how many reps is the calculator most accurate?
At 3-8 reps. With many reps, fatigue and endurance have an effect and the estimate drifts from the real maximum.
Is testing 1RM directly safe?
It can be risky for beginners. It is safer to use submaximal sets and estimate 1RM with a calculator, or to test only with a spotter and good technique.