One Rep Max Calculator: Estimate Your 1RM and 5RM

One rep max calculator

Weight lifted

Reps done (1 to 9)

Enter a recent set where you could not have done another rep with the same weight. Count only the reps you completed. Sets of 10 or more reps are not used.

Estimated one-rep max

Estimated five-rep max

Reps	Estimated weight
1
2
3
4
5
6
7
8
9

These numbers are estimates based on the set you entered, not measured maxes or prescribed loads. Use them as planning references, not instructions to attempt a maximum. If you use an estimate in training, adjust to how the set actually feels. Stop an exercise if it causes pain.

Designed for people who already lift and are entering a set of an exercise they already perform.

How it works. Enter a recent set where you could not have done another rep with the same weight. The calculator applies the Brzycki equation to that set: weight lifted / (1.0278 - 0.0278 × reps). Brzycki developed the equation for repetitions performed to fatigue and limited its use to fewer than 10 repetitions, so the calculator accepts 1 to 9 reps.

It then uses the same equation to work back to the estimated equivalent weight for each rep count from 1 to 9. Every number shown is rounded to the nearest 1 lb or 0.5 kg. Every result is an estimate. The calculation runs in your browser.

If you stopped the set with reps left, use the RPE calculator instead.

What 1RM and 5RM mean

Your one-rep max is the heaviest weight you can lift for a single rep with good form. Your five-rep max (5RM) is the heaviest weight you can lift for five reps. Both are specific to the exercise: a bench press max and a squat max are different numbers. The calculator estimates them from a set you already did.

Example

If your last set was 60 kg for 4 reps, the calculator shows an estimated one-rep max of 65.5 kg and an estimated five-rep max of 58 kg. For 225 lb for 3 reps, it shows 238 lb and 212 lb.

Why it stops at 9 reps

Brzycki limited his equation to fewer than 10 repetitions. In a study of bench press in women, Mayhew and colleagues (2008) found that prediction equations were more accurate when the sets used had fewer than 10 repetitions to fatigue. So the calculator accepts 1 to 9 reps.

One estimate per exercise

An estimate only applies to the exercise you entered. A squat set does not give you a deadlift estimate. For the barbell bench press, squat and deadlift, see the bench press, squat max and deadlift calculators.

Questions

What is a one rep max?

The heaviest weight you can lift for one rep of an exercise with good form. It is usually written as 1RM.

How do you calculate your one rep max?

Enter the weight and reps from a recent set where you could not have done another rep. The calculator applies the Brzycki equation to estimate your 1RM, then works back to the estimated equivalent weight for each rep count from 1 to 9.

What is a 5RM?

Your five-rep max: the heaviest weight you can lift for five reps.

How accurate is a one rep max calculator?

Treat the result as an estimate. It depends on whether the set really was to fatigue, and on the Brzycki equation, which Brzycki limited to fewer than 10 repetitions.

Can I enter 10 or more reps?

No. Brzycki limited his equation to fewer than 10 repetitions, so the calculator accepts 1 to 9.

My set was not to failure. What should I use?

The RPE calculator. Rate the set by how many reps you had left, and it accounts for them.

For coaches

Wolvec is an AI platform for fitness coaches and online personal trainers, the whole coaching setup rather than an add-on to it. Your AI drafts each program week based on how you coach and the client's intake, and you approve the week before the client sees it.

One rep max calculator