Weightlifting Tool to Calculate Your 1 Rep Max

1 Rep Max Calculator

I had published this post once before, but recently a couple people have asked for such a tool, so I’m busting it out again for all the new Project Swole readers.

There are many strength training programs that involve calculating your 1 rm or 1 repetition maximum. Some programs want you to use a % of your 1 rm, which is sometimes even harder to calculate.

1 Rep Max Calculator
Calculate Your 1 Rep Max

Most of us do not how how to figure out this number without performing the actual rep itself. Use this easy calculator to get a basic idea of how much weight you can lift once.


The problems with finding your 1 rep max by doing the actual reps:

  • If you do too many warm up sets or too many attempts, your 1 rm will be lower due to fatigue.
  • If you are having a bad day either in life or in the gym, your 1 rm will be lower due to stress.
  • If you are using steroids or supplements, your 1 rm will be higher due to the supplementation.

What I have provided here for you today, is a simple 1 rm calculator. Simply plug in the weight you used and the number of reps you completed before failure, without assistance, and you will have an idea of what your 1 rm is.

The problems with the calculator:

  • Everyone’s body is different. If you are built for endurance, the calculator result will be too high.
  • If you are built for absolute strength and explosive power, the calculator result will be too low.
  • You should use 3 different weights at 3 different rep ranges, and average those numbers to get a closer approximate result.

1 Rep Max Calculator

Enter weight lifted in pounds:

Enter number of reps (1-12):

50% –
55% –
60% –
65% –
70% –
75% –
80% –
85% –
90% –
95% –
Your 1 Rep Max:

Like I said, these numbers could be off depending on the way you train and your genetics. They are probably accurate within 10-20 pounds on either side, but these are the numbers I would suggest using in a weight lifting program, if you don’t already know your 1 rep max or any of the other percentages. Now go lift!

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