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One-Rep Max (Brzycki) Calculator

Reviewed by the CalculatorHub team, edited by James Graham. Brzycki 1RM formula. Last verified 15 June 2026.

The Brzycki formula is a widely cited method for estimating a lifter's one-rep maximum (1RM) from a submaximal set. Published by Matt Brzycki in 1993 in the Journal of Physical Education, Recreation and Dance, the formula is: 1RM = weight x 36 / (37 - reps). It is best used with rep counts between 2 and 10. Unlike testing an actual 1RM, submaximal estimation reduces injury risk and can be done as part of a normal training session. The calculator also displays common training percentages to help you set loads for strength, hypertrophy, and endurance blocks.

The weight you used for the set
Best accuracy at 2 to 10 reps; must be less than 37
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Brzycki 1RM formula

1RM = weight × 36 / (37 - reps)

Where weight is the load lifted and reps is the number of repetitions completed. The formula is undefined when reps equals 37 or greater. At reps = 1, the formula returns weight x 36/36 = weight exactly, which is the correct result (your 1RM is the weight itself). Accuracy decreases markedly above 10 reps.

Comparing 1RM formulas

  • The Epley formula (weight x (1 + reps/30)) tends to give slightly higher estimates at moderate rep counts.
  • The Brzycki formula tends to give slightly lower estimates at higher rep counts.
  • Both formulas are validated in peer-reviewed research and widely used by strength and conditioning coaches.
  • When in doubt, use the lower of the two estimates for safety when setting training loads near maximal intensity.

Brzycki 1RM calculator: frequently asked questions

What is the Brzycki formula?

The Brzycki formula estimates your one-rep max as: 1RM = weight x 36 / (37 - reps). It was published by Matt Brzycki in 1993 and is designed for use with rep counts of 1 to 10. The formula becomes undefined at reps = 37 and is unreliable above 10 reps.

How does Brzycki compare to Epley?

Both formulas are widely used and validated. The Brzycki formula tends to give slightly lower 1RM estimates than Epley at higher rep counts, and slightly higher estimates at lower rep counts. Most research finds both formulas similarly accurate in the 4 to 8 rep range.

Why does accuracy drop off above 10 reps?

At higher rep counts, local muscular endurance, cardiovascular conditioning, and mental fatigue play a larger role than pure strength. The relationship between load and rep capacity is not perfectly linear, so predictions become less reliable for high-rep sets.

Can I use Brzycki for powerlifting competition planning?

Many powerlifters use submaximal rep tests during training to estimate their 1RM and select opening attempts for competition. The Brzycki estimate is useful as a planning guide, but competition-day performance depends on readiness, peaking, and attempt selection strategy.

Should I always lift to failure to use this calculator?

You do not need to lift to absolute failure. Stopping one or two reps short of failure (called reps in reserve) and entering the weight and actual reps completed is adequate. Stopping just short of failure reduces injury risk while still providing a reliable estimate.

Official sources

  • Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation and Dance, 64(1), 88-90.
  • National Strength and Conditioning Association (NSCA): nsca.com.
  • American College of Sports Medicine (ACSM): acsm.org.

Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.