One Rep Max (1RM) Calculator
Estimate your one rep max for any lift using the Epley formula. Free 1RM calculator with percentage breakdown for training programs.
How this calculator works
This uses the Epley formula to estimate the most weight you could lift once from a set you already completed. The fewer reps in the set, the more accurate the estimate — a 3 to 5 rep set is the sweet spot.
Use the result to set working weights, not to chase a new max. Most productive training sits between 65 and 85 percent of your estimated one rep max.
Frequently asked questions
How accurate is a 1RM calculator?
Very close from sets of 3 to 5 reps. Accuracy drops as reps climb, because endurance starts to matter more than maximum strength.
Should I actually test my one rep max?
Rarely, and only with good technique and a spotter. An estimate from a heavy set of three gives you the same training information with far less risk.
What percentage should I train at?
Strength work usually sits at 80 to 90 percent for low reps; muscle-building work at 65 to 80 percent for 6 to 12 reps.
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