Sports calculator

One Rep Max Epley Calculator

Lifted weightRepetitions

Estimated 1RM: -

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Calculation explained

How this result was calculated

The formula, your substituted values, and the evaluated result are shown below.

Visual analysis

How the result changes when the first input changes

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This calculator applies the one rep max epley relationship. Enter values in the stated units and review the result. Check assumptions and use appropriate professional guidance for safety-critical decisions.

About this calculator

Calculate one rep max epley using clearly labelled inputs.

Calculator guide

How the one-rep max calculator works

Your one-rep max (1RM) is the heaviest weight you could lift once with good form. Testing it directly is tiring and carries some injury risk, so this calculator estimates it from a heavier set of several reps, using the Epley formula:

1RM = weight × (1 + reps ÷ 30)

Worked example: 80 kg bench press for 8 reps

80 × (1 + 8 ÷ 30) = 80 × 1.267 = 101.3 kg estimated 1RM

Training loads as a percentage of 1RM

Rearranged, the Epley formula also tells you roughly how many reps you can do at a given percentage of your 1RM: | Reps | Approx. % of 1RM | | 1 | 100% | | 3 | 91% | | 5 | 86% | | 8 | 79% | | 10 | 75% | | 12 | 71% |

So with an estimated 101 kg 1RM, a set of 5 would be about 86 kg.

How accurate is it?

Estimates are best from sets of about 2–10 reps taken close to failure. Beyond 10–12 reps, accuracy drops quickly.
Results vary by lift and by person. Some people have far more muscular endurance than others.
Other formulas (Brzycki, Lombardi) give slightly different numbers. Stick with one formula so your progress is comparable over time.

Using your 1RM safely

You don't need to test a true 1RM to train well. Use the estimate to set working weights, track progress every few weeks with the same lift and rep range, and use a spotter or safety bars on bench and squat. If you're new to lifting or have health conditions, get guidance from a qualified coach or physiotherapist.

Common mistakes

Using a set that wasn't close to failure, which underestimates your 1RM.
Using sets of 15+ reps, which gives unreliable estimates.
Comparing estimates from different formulas.

How do I calculate my one-rep max without testing it?

Lift a weight for 3–8 hard reps and use the Epley formula: weight × (1 + reps ÷ 30).

Is the Epley formula accurate?

It's reasonably accurate for sets of about 2–10 reps, but it's an estimate. Individual results vary.

What percentage of 1RM should I train at for strength?

Strength work is typically around 80–90% of 1RM for 3–6 reps. Muscle-building work is often around 65–80% for 6–12 reps.

Written by Sam Alex, civil engineer. About the author