One Rep Max Calculator

Your one rep max, or 1RM, is the most weight you can lift for a single repetition of an exercise with good form. It is the standard reference point for measuring strength and for setting training loads as a percentage of your max.

Both estimate a 1RM from a submaximal set. Epley uses weight times (1 + reps / 30), while Brzycki uses weight times 36 / (37 minus reps). They agree at around 10 reps and diverge slightly elsewhere, so this tool shows both and averages them.

Estimates are most reliable for sets of about 1 to 6 reps. As reps climb, fatigue and endurance vary more between people, so the formulas drift. This calculator caps reps at 12 because both equations lose accuracy beyond that and can overstate your true max.

Many strength programs prescribe loads as a percent of 1RM. Heavy strength work often sits near 85 to 95 percent, hypertrophy work around 65 to 80 percent, and warm-ups lower. Read the weight next to each percent in the table and load the bar accordingly.

An estimate is safer and good enough for programming most of the time. Testing an actual max carries more injury risk and needs a full warm-up, spotters and fresh recovery, so most lifters only do it occasionally, if at all.

No. The calculation runs entirely in your browser. The weight and reps you enter never leave your device.