HesapHanem

One Rep Max (Brzycki) Calculator

Estimate your 1RM the Brzycki way.

How it is calculated

The tool estimates the heaviest weight you could lift once from a set of several repetitions with the Brzycki formula: 1RM = w × 36 / (37 − r). Here w is the weight lifted (any unit, the answer comes back in the same unit) and r is the number of repetitions you completed. This is the same as dividing by 1.0278 − 0.0278 × r. One rep returns the weight itself. Reps must be a whole number from 1 to 36 and the weight above zero; a fractional rep count such as 8.5, or anything outside that range, gives no result. The result is rounded to two decimals. It is an estimate: it works best for sets of about 2 to 10 reps taken close to failure, and very high rep counts give inflated numbers.

Worked example

You lift 80 kg for 8 repetitions. Subtract the reps from 37: 37 − 8 = 29. Multiply the weight by 36: 80 × 36 = 2,880. Divide: 2,880 / 29 = 99.31. The calculator shows an estimated one-rep max of 99.31 kg. That is about 124 % of the weight you used for the set.

Try this example →

Common mistakes

  • Entering reps from a set that stopped far short of failure. The formula assumes you could not have done many more reps.
  • Trusting high-rep sets. The tool accepts up to 36 reps, but a set of 30 reps with 80 kg predicts a max of 411.43, which is unrealistic.
  • Entering a fractional rep count, such as 8.5 for a half rep. Only whole reps are accepted and the result is blank otherwise.
  • Mixing pounds and kilograms. The answer is in the unit you typed in.
  • Counting the warm-up weight rather than the working set's weight and reps.

About this calculator

The Brzycki formula — 1RM = weight ÷ (1.0278 − 0.0278 × reps) — estimates the maximum weight you could lift for a single repetition based on a lighter weight lifted for multiple reps, published by strength coach Matt Brzycki in a 1993 issue of the Journal of Physical Education, Recreation and Dance. It assumes a fairly linear relationship between reps performed and percentage of true 1RM, which holds reasonably well in the roughly 2-to-10-rep range but grows less accurate at very high rep counts.

Strength coaches and lifters use rep-max formulas like Brzycki's — alongside competing versions such as the Epley formula — to estimate a 1RM without the injury risk and fatigue cost of actually testing a maximal single lift, which is useful for programming training percentages (like setting a working weight at 75% of estimated 1RM) and tracking strength progress between true max-out sessions.

Was this helpful?

You can pick up to 3 reactions.

Comments

  • Be the first to comment.

Popular calculators

Loan Calculator

Monthly payment, total interest and full amortization schedule.

Percentage Calculator

Percent change, percent of, and ratio calculations.

Discount Calculator

Calculate final price, savings, and discount amount.

BMI Calculator

Body mass index from height and weight (metric or imperial).

Age Calculator

Compute your exact age in years, months and days from a birth date.

Compound Interest Calculator

Calculate the final amount and interest earned with compounding.

All Calculators