One-Rep Max Calculator

Estimate your one-rep max from a set, with useful training percentages.

Estimated 1RM (Epley)

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Brzycki estimate

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90% (~4 reps)

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80% (~8 reps)

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70% (~12 reps)

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A general estimate, not coaching or medical advice. Formulas are most accurate at low reps. Warm up properly, use good form, and get qualified guidance and a spotter before attempting heavy or maximal lifts.

Estimating a max without maxing out

Your one-rep max is the most you could lift once. Rather than testing it directly — which is risky — you can estimate it from a heavier-than-comfortable set using well-known formulas.

Epley: 1RM = w × (1 + reps ÷ 30)

These equations are fitted to real lifting data and work best at low rep counts. The calculator also shows common training loads as percentages of the estimate, which is how many strength programmes prescribe weights.

Worked example

Lifting 100 kg for 5 reps estimates a one-rep max of about 116.7 kg by the Epley formula, or 112.5 kg by Brzycki. Working sets at 80% would be around 93 kg.

Using it in training

A reliable estimate lets you plan loads sensibly without grinding out true singles every week. Re-estimate from your working sets as you progress, and let the range between the two formulas remind you that it is a guide, not a guarantee.

Train smart

Lower reps, better estimate. A heavy set of 3–5 predicts more accurately than a set of 15.
Form first. A clean rep is the only rep that counts toward an honest figure.
Build up. Warm up thoroughly and progress gradually; get coaching for heavy attempts.

This is general information, not medical advice.

Frequently asked questions

How reliable is an estimated 1RM?

It is an estimate. Formulas are most accurate at lower rep counts — say 1 to 6 — and drift as reps climb, since endurance and technique start to dominate. Treat it as a guide.

Why do Epley and Brzycki differ?

They are different equations fitted to data, so they disagree slightly. Showing both gives a sensible range rather than a single false-precision number.

What are the percentages for?

Programmes often prescribe loads as a percentage of 1RM — for example heavier triples near 90% or volume work around 70%. The table makes those easy to read off.

Should I actually test my true 1RM?

A real max attempt carries injury risk and needs proper warm-up, technique and ideally a spotter. Estimating from a comfortable set is a safer everyday approach.