One-Rep Max (1RM) Calculator

Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. Rather than testing it directly (which carries injury risk), this calculator estimates it from a sub-maximal set using the Epley formula - one of the most validated 1RM prediction equations.

kg

The weight you used for your working set.

Keep reps at 10 or fewer for best accuracy.

Estimated 1RM
116.7 kg
95%
110.8 kg
90%
105 kg
85%
99.2 kg
80%
93.3 kg
75%
87.5 kg
70%
81.7 kg

How it works

Enter the weight and number of reps from a recent heavy set (ideally 3-10 reps). The Epley formula extrapolates your theoretical maximum. The table below shows training weights at standard percentages of that max.

Formula
1RM = Weight x (1 + Reps / 30) (Epley formula)

Example. Lifting 100 kg for 5 reps gives an estimated 1RM of 116.7 kg. Your 80% training weight would then be 93.3 kg.

Frequently asked questions

Is the Epley formula accurate?

Yes, for most people within 5-10% when using 3-10 rep sets. Accuracy decreases for very high rep sets (10+). For the bench press, squat and deadlift specifically, it performs very well.

Why not just test my actual 1RM?

Maximal single-rep lifts carry higher injury risk, require a spotter and tax the nervous system significantly. Estimated 1RMs from working sets are safer and sufficient for programming purposes.

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