1RM calculator

Work out your 1RM.

Enter the weight and reps of a set you did, and the calculator works out your estimated one-rep max (1RM) and what you should manage for other rep counts.

Weight (kg)

Reps

–kg

Estimated 1RM

Percentage of 1RM

Reps	% of 1RM	Weight
1	100 %	–
2	97 %	–
3	94 %	–
4	92 %	–
5	89 %	–
6	86 %	–
7	83 %	–
8	81 %	–
9	78 %	–
10	75 %	–
11	73 %	–
12	71 %	–

What is a 1RM?

Your 1RM (one-repetition maximum) is the heaviest weight you can lift once with good form. Testing it directly is demanding and raises the risk of injury, so most lifters estimate it from a heavy set of 2–10 reps.

How it is calculated

The calculator averages two common formulas: Epley (weight × (1 + reps / 30)) and Brzycki (weight × 36 / (37 − reps)). Both are most accurate up to about 10 reps; beyond that the estimate gets loose.

Using your 1RM in training

Strength: 80–90% of 1RM, 3–6 reps.
Muscle growth: 65–80% of 1RM, 6–12 reps.
Technique and warm-ups: 40–60% of 1RM.

Stave does this after every set

Stave estimates your 1RM for every set you log, marks new records and suggests your next weight from how you actually respond to reps and weight. A free gym log for strength training.

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