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One Rep Max Calculator

Estimate your 1RM from a set, plus a full percentage table.

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Formula estimates

Seven published formulas. The spread between them is the honest error bar.

FormulaEstimated 1RMvs average

Training percentages

%WeightTypical repsTrains

Estimated one rep max

—

Confidence

Formula range—
Reliability—
Set intensity—

Common working sets

Strength — 85%—
Hypertrophy — 75%—
Endurance — 60%—

Estimates are most reliable for sets of two to five reps and degrade quickly above ten, where the formulas begin measuring muscular endurance rather than maximal strength. Warm up properly and never treat a calculated number as a weight you are certified to lift.

Quick Tool Overview

The One Rep Max Calculator estimates your 1RM from a set you have already done, using seven published formulas at once so you can see how much they disagree. A percentage table turns the result into working weights for strength, hypertrophy and endurance training.

What it does
Estimates a one rep max from a submaximal set
You give it
The weight lifted and the number of clean reps
You get back
Seven formula estimates, an average and a percentage table
Best for
Programming training percentages without testing a true max
Calculators Free, unlimited use No sign-up Runs in your browser

About the One Rep Max Calculator

Estimate your one rep maximum from a set you have actually done, without having to test a true single. Enter the weight and the number of reps, and seven published formulas are calculated together so you can see how much they disagree.

One rep max is the reference point most programming is written against, since training percentages, load progressions and competition attempts all key off it. The estimate is at its best in the two-to-five rep range and degrades quickly past about ten, where the formulas start measuring your endurance rather than your strength. The percentage table below the result turns the number straight into working weights for strength, hypertrophy and endurance blocks.

Key features of the One Rep Max Calculator

Seven formulas at once

Epley, Brzycki, Lombardi, O Conner, Wathan, Mayhew and Lander, shown together with their average.

Percentage table

Working weights from 50 to 100 percent of the estimate, with the rep range each load typically allows.

Accuracy stated plainly

The tool says the estimate is best at two to five reps and degrades above ten, rather than implying equal confidence everywhere.

Avoids max testing

A true single carries injury and fatigue costs that a submaximal estimate sidesteps entirely.

Kilograms or pounds

Switch units without re-entering anything.

How to use the One Rep Max Calculator

  1. 1

    Enter the set you did

    The weight lifted and the number of clean reps, in kilograms or pounds.

  2. 2

    Compare the formulas

    Epley, Brzycki, Lombardi, O Conner, Wathan, Mayhew and Lander are shown together with an average.

  3. 3

    Read the percentage table

    Working weights from 50 to 100 percent, with the reps each load typically allows.

  4. 4

    Use the lower reps

    Sets of two to five give the most reliable estimate. Above ten reps, treat the number as indicative only.

Frequently asked questions

Within a few percent for sets of two to five reps, and progressively worse above that. At ten or more reps the formulas diverge widely because they are partly measuring muscular endurance.

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