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Estimated One-Repetition Maximum

Estimate an approximate one-rep max from a submaximal set, using the Epley formula.

What this answers:

  • Given a weight and rep count I actually lifted, what's an approximate one-rep-max estimate?

This is an illustrative estimate, not a validated maximum for any individual, and this tool does not instruct unsafe maximum-weight attempts. Supported for 1–10 reps in this version; accuracy varies by exercise and individual.

How it's calculated

1RM = load × (1 + reps/30) for 2–10 reps; 1 rep returns the entered load unchanged.

Worked example

60 kg for 5 reps: 60 × (1 + 5/30) = 70 kg estimate.

Formula version: Epley (versioned, v1). Source: peer-reviewed literature on 1RM prediction equations and their limitations. Source last checked September 28, 2026.

Weight units and input

This version accepts and reports weight in kilograms only. If your gym tracks pounds, convert before entering a value (1 kg ≈ 2.2046 lb) — see our unit converter for a general-purpose conversion tool.

FAQ

One-Rep Max Calculator: Frequently Asked Questions

Testing a true one-rep max requires lifting the heaviest weight you can move for a single rep, which carries meaningfully more injury risk than a submaximal set — especially without a spotter or coach present. Estimating from a lighter, higher-rep set most people can perform safely is the practical reason prediction formulas like Epley's exist.

Prediction equations like Epley's are built from, and validated against, submaximal sets in roughly this range. Beyond about 10 reps, the set is measuring muscular endurance more than near-maximal strength, and the estimate becomes considerably less reliable — so this tool doesn't extrapolate past it.

Yes. These equations are most studied on large compound barbell lifts (e.g. bench press, back squat, deadlift) and tend to be less reliable for isolation exercises or machine-based movements, where fatigue and form can behave differently across a rep range.

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