How 1RM is estimated
The Epley formula is weight × (1 + reps ÷ 30); Brzycki is weight × 36 ÷ (37 − reps). They agree closely at low rep counts and diverge as reps climb, which is why this calculator averages them and warns above fifteen.
Accuracy is best from sets of two to five taken close to failure. A set of twelve depends heavily on muscular endurance, which varies far more between people than maximal strength does.
Using the percentage table
Most strength programmes prescribe load as a percentage of 1RM. The table above converts your estimate into working weights and the rep count each percentage typically supports.
Treat it as a starting point that needs adjusting. Bench press and squat percentages behave differently — most lifters can complete more reps at a given percentage on squats than on bench.
Frequently asked questions
Should I test my actual 1RM? +
Rarely, and only with experience and a spotter. True maximal attempts carry real injury risk and require days of recovery; estimating from a heavy triple gives nearly the same information at a fraction of the cost.