What is the Brzycki formula and who developed it?

Matt Brzycki published this linear regression equation in 1993 to estimate one-rep max from sub-maximal lifts. It uses the constants 36 and 37, derived from observed strength data, to extrapolate maximal capacity without requiring a true 1RM test.

Why does accuracy drop above 10 reps?

As repetitions increase beyond 10, muscular endurance and lactate tolerance become limiting factors rather than pure maximal strength. The Brzycki formula assumes a consistent strength-to-endurance relationship that holds best in the 2–10 rep range.

Can I use this for Olympic lifts or explosive movements?

The Brzycki formula was developed using slow-tempo barbell exercises like bench press and squat. Olympic lifts involve technical skill and bar speed that are not captured by rep-based regression, so prediction error may be higher.

How does Brzycki compare to other 1RM formulas?

Brzycki tends to produce slightly higher estimates than Epley or Lander formulas in the mid-rep range. Research shows no single equation is universally superior; individual variation and exercise type both influence which model tracks closest to measured 1RM.

Should I test my actual 1RM or rely on the estimate?

Estimated 1RM values serve as planning benchmarks and training-load references. Direct 1RM testing offers precise data but introduces fatigue and injury risk; many programs use sub-maximal estimates to inform percentage-based programming while reserving true max tests for competition or periodic assessment.

Strength Training

One-Rep Max Calculator (Brzycki Formula)

Estimate your one-rep max from sub-maximal lifts using the Brzycki (1993) formula.

Last updated: 22 April 2026

What this tool does

This calculator estimates your one-repetition maximum (1RM) using the Brzycki formula, a linear regression model published in 1993 and widely applied in strength training. It requires the weight lifted and the number of repetitions performed (up to 36 reps) and outputs an estimated maximum weight that could be lifted for a single repetition. The formula was derived from barbell-exercise data in trained lifters and is most accurate when reps are kept below 10, as prediction error tends to increase with higher repetition ranges.

Inputs

Result

—

Formula Used

1RM = w \times \frac{36}{37 - r}

w

Weight in kg

r

Reps performed

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How One-Rep Max Calculator (Brzycki Formula) works

This calculator estimates a lifter's one-repetition maximum (1RM) from a sub-maximal set by applying the Brzycki formula. Enter the weight lifted and the number of repetitions performed to technical failure, and the tool returns an estimated 1RM. The Brzycki equation uses a fixed linear coefficient to extrapolate maximal strength from lighter loads, making it a quick field method when direct 1RM testing is impractical or unsafe.

The formula

The Brzycki (1993) formula is:

1RM = weight × 36 / (37 - reps)

Where weight is the load lifted (in kilograms or pounds) and reps is the number of repetitions completed. The constants 36 and 37 are derived from regression analysis of observed sub-maximal-to-maximal strength relationships in trained lifters.

Where this method is most accurate

The Brzycki formula shows the highest agreement with measured 1RM when repetitions fall between 2 and 10. Below 2 reps, the estimate approaches the actual test weight; above 10 reps, fatigue and muscular endurance begin to dominate, and prediction error typically increases. The equation was developed using bench press and squat data from moderately trained populations, so accuracy may vary with exercise selection, training experience, and individual fiber-type distribution.

What this tool does not do

This calculator produces a mathematical estimate, not a prescription or training program. It does not account for daily fatigue, injury history, bar speed, technique variation, or concurrent training stress. The tool does not diagnose strength deficits, recommend loads for programming, or guarantee performance outcomes. It is intended for informational exploration—users remain responsible for validating results against actual lifting conditions and consulting qualified coaches for program design.

Disclaimer

This tool is for educational and informational purposes only. It is not a substitute for professional coaching, medical advice, or individualized program design. All strength training carries inherent risk; consult a qualified professional before attempting maximal or near-maximal lifts.

Questions

What is the Brzycki formula and who developed it?: Matt Brzycki published this linear regression equation in 1993 to estimate one-rep max from sub-maximal lifts. It uses the constants 36 and 37, derived from observed strength data, to extrapolate maximal capacity without requiring a true 1RM test.
Why does accuracy drop above 10 reps?: As repetitions increase beyond 10, muscular endurance and lactate tolerance become limiting factors rather than pure maximal strength. The Brzycki formula assumes a consistent strength-to-endurance relationship that holds best in the 2–10 rep range.
Can I use this for Olympic lifts or explosive movements?: The Brzycki formula was developed using slow-tempo barbell exercises like bench press and squat. Olympic lifts involve technical skill and bar speed that are not captured by rep-based regression, so prediction error may be higher.
How does Brzycki compare to other 1RM formulas?: Brzycki tends to produce slightly higher estimates than Epley or Lander formulas in the mid-rep range. Research shows no single equation is universally superior; individual variation and exercise type both influence which model tracks closest to measured 1RM.
Should I test my actual 1RM or rely on the estimate?: Estimated 1RM values serve as planning benchmarks and training-load references. Direct 1RM testing offers precise data but introduces fatigue and injury risk; many programs use sub-maximal estimates to inform percentage-based programming while reserving true max tests for competition or periodic assessment.

Sources & Methodology

Applies the Brzycki (1993) formula: 1RM = weight × 36 / (37 - reps). This linear regression model estimates maximal strength from sub-maximal repetitions, using fixed coefficients derived from barbell-exercise data in trained lifters.

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