One-Rep Max (1RM) Calculator
Estimate your one-rep max from weight and reps, with a percentage table for training β in your browser.
π Runs entirely in your browser. Your input and output are never sent to a server or stored β fully private.
Estimates only β not medical advice.
About this tool
Want to know your top lift without risking a true max attempt? Enter the weight you lifted and how many clean reps you managed, and this calculator estimates your one-rep max (1RM) using the Epley and Brzycki formulas. It also prints a percentage table so you can read off training loads β say 80 percent for sets of eight. Lifters use it to set weights and track strength over time. The estimate is computed in your browser, so nothing you enter is uploaded.
Frequently asked questions
Which formula should I use?
Both are well established and usually land within a few percent of each other. Epley calculates weight Γ (1 + reps / 30), while Brzycki uses weight Γ 36 / (37 β reps). Epley tends to read a touch higher at high rep counts. They are most accurate for sets of one to ten reps; beyond about ten the estimate drifts, so a heavy set of three to five gives the best prediction.
How do I use the percentage table?
Once your 1RM is estimated, the table shows common training percentages and the reps you can typically hit at each β for example around 100 percent for one rep, 90 percent for about four, and 75 percent for roughly ten. Pick the load that matches your session's goal: heavier percentages for strength, lighter ones for higher-rep volume work.
Is the estimate safe to load on the bar?
Treat it as a guide, not a guarantee. A true max depends on technique, fatigue, sleep and the lift itself, so always warm up, use a spotter or safeties, and build up gradually rather than jumping straight to the predicted weight. If you are new to lifting or have an injury, get advice from a qualified coach or clinician. The maths runs locally in your browser with nothing uploaded.