Your one-rep max: the heaviest weight you can lift once, with correct form, in a given exercise.

Is testing my real 1RM dangerous?

It carries more risk than a set of several reps and calls for good form, a warm-up and safety (safety bars or someone spotting you). That is why many people prefer to estimate it.

Does it work for pull-ups or dips?

With a caveat: the weight that counts is your body plus any added load, because that is what you move. Enter the sum as the weight lifted.

One-rep max calculator: estimate your 1RM

Type the weight and reps of a hard set and you get your estimated 1RM: the most you could lift once. It uses the Epley formula (weight × (1 + reps ÷ 30)). With 100 kg for 5 reps, that comes to 116.7 kg.

Weight lifted (kg)Reps doneReps you had left (RIR)Optional. If you finished at your limit, leave it at 0.

Your estimated 1RM

116.7 kg

Estimated weights for each number of reps
Reps	Weight	% of 1RM
1	116.7 kg	100 %
2	109.4 kg	94 %
3	106.1 kg	91 %
4	102.9 kg	88 %
5	100 kg	86 %
6	97.2 kg	83 %
8	92.1 kg	79 %
10	87.5 kg	75 %
12	83.3 kg	71 %
15	77.8 kg	67 %

Calculated in your browser. Nothing you type is sent anywhere.

How to get a useful estimate

Use a set of 2 to 10 reps done with good form. The closer to a single rep, the more reliable it is.
Warm up first and do not use a set from the end of a long session: when you are tired, the number comes out below your real best.
If you had reps left, enter them in the RIR field. With 100 kg for 5 reps and 2 in reserve, the sum uses 7 reps.
Always compare the same exercise and the same form. A higher squat gives a different number, not progress.

Which formula it uses and how far it goes

Epley is one of the most widely used, and it is the one GoForIt uses for its estimated 1RM. All these formulas are approximations: they come from the average relationship between weight and reps, which changes from person to person and from exercise to exercise. Treat it as a reference for setting loads, not as a record.

What the number is for

Choosing the weight in a programme written in percentages, seeing whether you are progressing without doing a true max, and comparing weeks even when the reps were different. If you train by feel, combine it with RPE and RIR. Before the heavy set, the warm-up calculator gives you the ramp and the plate calculator says what to put on the bar.

Frequently asked questions

What is a 1RM?: Your one-rep max: the heaviest weight you can lift once, with correct form, in a given exercise.
Is testing my real 1RM dangerous?: It carries more risk than a set of several reps and calls for good form, a warm-up and safety (safety bars or someone spotting you). That is why many people prefer to estimate it.
Does it work for pull-ups or dips?: With a caveat: the weight that counts is your body plus any added load, because that is what you move. Enter the sum as the weight lifted.