If you've ever pulled a "one-rep max" estimate from a spreadsheet or calculator app, there's a good chance one of two formulas was running under the hood: Epley (1985) or Brzycki (1993) . They look similar on paper but give different answers under fatigue. Which matters when you're programming ...
Source: [Dev.to](https://dev.to/ffmicheck/the-two-1rm-formulas-that-give-different-answers-and-which-one-to-trust-8ib)