One Rep Max Calculator

Estimate your one rep max (1RM) from any set. 7 formulas, accuracy range, training percentages and warm-up. Free, works offline.

Estimate your one rep max (1RM) from any set you have already done, without putting a maximal bar on your back. Pick your lift, enter the weight and reps, and get an estimated max with an honest accuracy range, not one falsely precise number. WHAT YOU GET • An estimated 1RM with a likely range and a confidence level • 7 published formulas side by side (Epley, Brzycki, Lombardi, Mayhew, O'Conner, Wathan, Lander), with the best method chosen for your rep count • A percentage table: what to lift for strength, muscle size or endurance • A rep-max table from 1 to 12 reps • A warm-up ladder and meet-attempt suggestions • Optional RPE input, so sets that stopped short of failure still give a useful estimate • 28 lifts: barbell, dumbbell, machine and bodyweight, with sled weight, per-dumbbell weight and added-weight handling built in • kg and lb, one-click copy of your result PRIVATE AND SIMPLE No account, no ads, no tracking. Everything is calculated on your device. The extension asks for no browser permissions and makes no network requests. It only remembers your last inputs on your own computer. GOOD TO KNOW Estimates are not tested maxes. They are most accurate from hard sets of 2 to 6 reps. This extension is for general information, not medical advice. Use safety equipment or a spotter for heavy lifts, and speak to a doctor before starting a new training program if you have a health condition. Uses the same calculation engine as repmaxcalculator.one, where you will also find charts, guides and calculators for individual lifts.