One Rep Max Calculator

Method, assumptions & sources

Who this is for

Adults with a previously completed resistance exercise set. No new maximal test is required.

How it works

For load W and reps R: Epley W(1+R/30); Brzycki W/(1.0278−0.0278R); Lombardi WR^0.1; Mayhew 100W/(52.2+41.9e^(−0.055R)); O’Conner W(1+0.025R); Wathen 100W/(48.8+53.8e^(−0.075R)); Lander 100W/(101.3−2.67123R). A completed one-repetition set returns the recorded load for every model.

Keep in mind

• Different exercises and training histories produce different prediction errors.
• An estimate is not a safe load instruction. Use qualified supervision for strength testing.

Sources

• LeSuer et al. (1997): accuracy of seven 1RM prediction equations (opens in a new tab)
• Research comparison: empirical repetition prediction equations (opens in a new tab)