Calculate One Rep Max (1RM)

What Does One Rep Max Mean?

The term ‘One Rep Max’ (one repetition maximum) refers to an approximate measure of the maximum weight an individual can lift, on a single repetition, of an exercise. One Rep Max (1RM) is a good means of measuring maximum strength, and is usefull for guaging progress in a particular exercise. 1RM can also be used to determine the amount of load for an exercise, for example a powerlifter may concentrate on lifting at 85% of his/her 1RM. Whereas someone looking for definition may concentrate on 70% 1RM.

Why Calculate One Rep Max?

Determining the maximum weight you are capable of liting is important for a number of reasons:

  • It allows you to guage progress in a particular exercise.
  • Enables you to calculate your Relative Strength Ratio. For example, if a 100kg male acheives a one rep max of 140kg on barbell squats, his Relative Strength Ratio would be 1.4. This value can then be used to rank that individuals performance on that particular exercise in comparisson to other exercises he completes in that session.
Formula for Calculating One Rep Max

Formula to calculate One Rep Max

How is it Calculated?

A lifter can calcute One Rep Max (1RM) for an exercise using the formula shown, where r is the number of repetitions performed, and w is the weight lifted.

Calculate One Rep Max

Enter your info below, to calculate One Rep Max.


If done correctly, taking the time to calculate One Rep Max is almost definitely worth your while when it comes to guaging progress, and also for getting the most out of your training programme. While it is quite safe to use this calculator alone, if you’re going to attempt to calculate One Rep Max for real in the gym, you should definitely take a spotter with you! And don’t forget to work through 2 – 3 warm up sets before attempting to lift your 1RM.


1 ping

  1. Jan Korb

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  2. Alan Bradley

    Thanks for the help man. Very useful blog!

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