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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Project Swole is managed and mostly written by Steve, a formerly IFPA and ISSA certified personal trainer and sport nutritionist, who has been studying, practicing, and experimenting with fitness and nutrition since 1992. Please use the content at Project Swole to supplement the advice of your doctor or physician. All medical questions should be directed towards a qualified medical professional, and the advice provided at Project Swole should be used at your own discretion.

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8 Responses to “Weightlifting Tool to Calculate Your 1 Rep Max”

  1. [...] 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. read on [...]

  2. Todd says:

    Steve, this looks like a great tool to have access too. Thanks. I’ll be adding a link to it from my blog. BTW, that picture is awesome!

  3. [...] over at Project Swole has a great calculator that lets you figure it out on the computer. Enter in the amount of weight that you can move for a [...]

  4. Danny says:

    Thanks, Steve. Keep up the good work…

  5. Chris Watson says:

    Thanks this is very useful, i have bookmarked it

  6. [...] Weightlifting Tool to Calculate Your 1 Rep Max (projectswole.com) [...]

  7. [...] Weightlifting Tool to Calculate Your 1 Rep Max (projectswole.com) [...]

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