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MasterMath

One Rep Max Calculator

Estimate the most you could lift once from an ordinary set, and get your training percentages out of it.

Your one-rep max

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Your one-rep max—
By Epley—
By Brzycki—
Gap between the formulas—

Loads by percentage of your max

PercentageWeightApproximate repetitions

How this was worked out

    Indicative result. This is an estimate from one set. The only exact way to know your one-rep max is to attempt it, and that needs a warm-up, solid technique and preferably someone spotting you.

    The formula

    Epley: 1RM = weight × (1 + reps ÷ 30) · Brzycki: 1RM = weight × 36 ÷ (37 − reps)

    Where it comes from

    Both formulas were fitted against real lifting data and agree closely up to about ten repetitions. Past that they diverge, because the relationship between weight and repetitions stops being linear and muscular endurance matters more than maximum strength. That is why both figures are shown rather than an average that would hide the gap.

    How to work it out by hand

    1. Note the weight and repetitions of a set taken close to failure
    2. Apply Epley: weight × (1 + repetitions ÷ 30)
    3. Apply Brzycki: weight × 36 ÷ (37 − repetitions)
    4. Take the average of the two as the estimate

    What is worth knowing

    The estimate only holds if the set was taken close to failure: with two or three repetitions left in reserve, the result comes out low. And reliability drops below six repetitions as much as it does above twelve. On the percentage table: maximum strength is trained above 85 %, hypertrophy between 65 and 80 %, and muscular endurance below 60 %.

    Frequently asked questions

    How is a one-rep max calculated?

    With Epley's formula (weight × (1 + reps ÷ 30)) or Brzycki's (weight × 36 ÷ (37 − reps)).

    Which of the two formulas is better?

    They agree almost always up to ten repetitions. Above that, Brzycki tends to come out low and Epley high.

    How many repetitions give the most reliable estimate?

    Between six and ten, with the set taken close to failure. Many repetitions cost the estimate its precision.

    What percentage should I train at?

    Above 85 % for maximum strength, 65 to 80 % for hypertrophy and below 60 % for endurance.