1RM Calculator (Brzycki)

Brzycki: estimating 1RM from a submaximal set

The Brzycki formula (Matthew Brzycki, 1993) turns any submaximal set into a 1RM estimate: 1RM = weight · 36/(37 − reps). The error stays under 5% from 1 to 10 reps and falls apart past 12. Example: 80 kg × 5 reps → 1RM = 80·36/(37−5) = 80·36/32 = 90 kg. Set that against Epley peso·(1+reps/30): 80·(1+5/30) = 93.3 kg. The two formulas land close together around 3-5 reps and drift apart as reps climb, with Brzycki running a touch more conservative than Epley through the medium range.

Applications: percentage-based training and powerlifting

It's a staple of percentage-based training (Jim Wendler 5/3/1, Sheiko, The Cube), where Brzycki does the math that turns a recent rep set into a working 1RM. In powerlifting prep it's handy for calling openers and second attempts without putting yourself through a true 1RM test, which piles on fatigue and injury risk. Strength-and-conditioning coaches also lean on it to track progress from one mesocycle to the next.

FAQ

Brzycki or Epley? Through 10 reps the two agree to within 2-3%. Beyond that, Epley starts overshooting harder. For powerlifting, Brzycki is the classic call.

Best rep range to estimate? Somewhere between 3 and 8 reps taken to near-maximal effort (RPE 9-10). Easy sets pull the estimate down.

Does it work for any lift? It holds up on the big compounds (squat, bench, deadlift, overhead press). On isolation work, technique shifts too much between rep ranges for the formula to apply cleanly.