REP MAX AND % CALCULATOR Find out your REP MAX and % for any lift using this calculator. This calculator estimates the potential number of reps, based on the specified data. In the training program, we can often see the exercise load as a percentage based on 1RM, which we don't know, but we have the experience of doing this exercise, for example, 4 or 6 reps. Testing your 1RM can be a pretty intense, and it requires a high degree of caution in order to avoid injury. As a result, we will be able to understand the potential 1RM and calculate the percentage of this weight to 1RM. Remember: these are only estimates.