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One Rep Max (1RM) Calculator

Calculate your estimated one-rep max using the average of 7 peer-reviewed formulas, and get training percentages for all your lifts

Your Lift

How to use:

  1. Enter the weight you lifted
  2. Enter how many reps you completed
  3. Get your estimated 1RM and training zones
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Enter your lift details to calculate 1RM

Methodology and Sources

We average 7 peer-reviewed formulas developed between 1985 and 1993 for the most robust estimate. Each formula has different accuracy depending on rep range and training level:

Epley (1985)

1RM = w * (1 + r / 30)

Brzycki (1993)

1RM = w * 36 / (37 - r)

Lander (1985)

1RM = 100 * w / (101.3 - 2.67123 * r)

Lombardi (1989)

1RM = w * r ^ 0.10

Mayhew et al. (1992)

1RM = 100 * w / (52.2 + 41.9 * e^(-0.055 * r))

O'Conner et al. (1989)

1RM = w * (1 + 0.025 * r)

Wathan (1994)

1RM = 100 * w / (48.8 + 53.8 * e^(-0.075 * r))

LeSuer, D.A., McCormick, J.H., et al. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research, 11(4), 211-213.

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Important Note

This calculator provides estimates only. Always use proper form and have a spotter when attempting heavy lifts. Consult with a qualified trainer before maxing out.