Brzycki Formula Calculator for 1RM

The Brzycki formula estimates a one rep max as weight × 36 ÷ (37 − reps). Matt Brzycki published it in 1993 as a practical tool for coaches who needed a max without testing for one. Enter your set below; the calculator prints Brzycki alongside Epley for comparison.

Worked example

Take 176 lb (80 kg) for 8 reps:

80 × 36 ÷ (37 − 8) = 2,880 ÷ 29 = 99.3 kg, or about 219 lb.

Journals normally print the same equation as weight ÷ (1.0278 − 0.0278 × reps). Multiply both parts by 36 and you are back to the version above — same numbers, different notation.

The wall at 37 reps

Brzycki’s denominator shrinks by one for every rep you add. At 30 reps it is down to 7, and the estimate has run away to more than five times the bar weight. At 37 it hits zero and the formula collapses. So the popular description of Brzycki as “the conservative one” is only true in a narrow band: it sits below Epley from 10 reps up to the low twenties, then crosses back over and overshoots dramatically. Below 10 reps it reads slightly higher than Epley. The two are equal at exactly 10.

None of this is a defect to route around — it is a signal that the equation has a working range, and that the range is short sets.

The rep range where it holds up

Mayhew’s team tested 14 published equations against measured bench press maxes in 103 women. Across the full range of reps to fatigue, Brzycki was one of only two linear equations whose predictions failed to correlate strongly with the real max. Restrict the analysis to sets of 10 reps or fewer and it flips: after training, Brzycki was among the best of the 14, landing within 2.3 kg of the true max for 58% of lifters. Same equation, different input discipline.

A 2026 preprint that fitted 303,494 near-failure sets across 388 exercises found the same structural limit in all the classics. Brzycki behaves as if every lift converted reps to load at the same fixed rate; light isolation work does not, and that is where its error concentrates.

Compare the models directly on Epley vs Brzycki, run the linear alternative on the Epley formula calculator, or average both on the one rep max calculator. To apply the result to a specific lift, start with the bench press max calculator.