CALCULATOR 10

One Rep Max Calculator

Estimate your one-rep max from a set of up to 15 reps, and get training weights by percentage.

Estimated 1RM

Enter the weight you lifted.

For general information only; not medical advice. Consult a qualified professional before making health decisions.

How this is calculated

w = weight lifted, r = reps

Epley (default)  w × (1 + r ÷ 30)
Brzycki          w × 36 ÷ (37 − r)
Lombardi         w × r^0.10
O'Conner         w × (1 + 0.025 × r)
Lander           100 × w ÷ (101.3 − 2.67123 × r)
Mayhew           100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r))
Wathan           100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r))

With 1 rep, every formula returns the weight lifted. Above 10 reps estimates get less accurate; above 15 they aren't given.

Sources

Epley B (1985); Brzycki M (1993); Lombardi VP (1989); O'Conner B et al. (1989); Lander J (1985); Mayhew JL et al. (1992); Wathan D (1994) — 1RM estimation.

What a one-rep max is

Your one-rep max (1RM) is the heaviest weight you can lift once with good form. Many strength programmes set training weights as percentages of it—for example, three sets of five at 80%.

Read more about the 1 Rep Max calculator

Why estimate instead of testing

Testing a true max is tiring, needs a spotter or safety equipment, and carries more injury risk—especially if you're newer to lifting. An estimate from a hard set of several reps gets you close enough to program from, and you can update it every few weeks as you get stronger.

Getting a good estimate

Use a set taken close to failure with clean technique. Sets of about 3 to 8 reps give the most reliable estimates; above 10 reps, fatigue and muscular endurance start to muddy the picture, which is why the calculator warns you there and stops at 15. Formulas also differ in how they treat higher reps, so the average of all seven is shown next to the Epley headline.

Using the percentage table

The table lists weights from 100% down to 50% of your estimated max, with typical reps you could complete at each—for example, around 8 reps at 80%. Plate rounding snaps weights to 2.5 kg or 5 lb steps so they match what you can load on the bar.

Frequently asked questions

How accurate is a 1RM calculator?

From a hard set of 3–8 reps, estimates are usually within a few percent of a tested max. Accuracy drops above 10 reps and varies between lifts and people.

Which 1RM formula is best?

Epley and Brzycki are the most widely used and agree closely at low reps. Because no formula is best for everyone, the calculator also shows the average of seven formulas.

How many reps should I use to estimate my 1RM?

Use a set of 3 to 8 reps taken close to failure with good form. Lower reps generally give more accurate estimates.

How do I use percentages of 1RM in training?

Programmes often prescribe work at a percentage of your max—for example 70–85% for strength and muscle building. Use the table to find the weight, and round to your available plates.