One Rep Max Calculator

Every method encodes the same idea: the more reps you can do at a weight, the smaller that weight is as a fraction of your max. Enter an all-out set — say 225 × 5 — and the formula works backwards to the single. Sets of 2–6 reps estimate most reliably; past 10 reps every formula gets fuzzy.

They agree within a few pounds at low reps and drift apart as reps climb. Brzycki tends to fit heavy triples and fives best; Epley is the most widely used all-rounder. That's exactly why this calculator shows them side by side — the spread itself tells you how confident to be.

Classic formulas assume nothing was left in the tank. If you had a rep or two in reserve, use the RPE calculator instead — it takes RPE into account so an honest RPE 8 set still gives a good estimate.

Estimates are for planning; testing is for meets and milestones. Most training decisions only need a good estimate, which is why coaches program off estimated maxes and save true max attempts for when they count.

That's the app: a free account saves each lift's 1RM with dated history, turns reps + RPE into working weights, builds warm-up ramps, and shows exactly which plates to load — using whichever calculation method you pick in Settings.