Wrist Size as a Predictor of Bicep Potential

I’m a 22 yo male, 5’7 and I have very small wrists. I measured them to be 5.5 inches. I used the Casey Butt formula calculator and the results show that the maximum bicep size I can achieve is 12.54 inches. Is this realiable ?

You can build much bigger biceps than that.


I think of Dexter Jackson the first time I saw him on stage. He had small joints and large long muscle bellies. Get this. He was a bantamweight in a National Qualifier. He won the Overall. I have a feeling that his wrists were very small.

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Are you currently training in any format?


I lifted for 20 years and built, by many accounts , an amazing physique before I knew there was even anything to know.

Then I found the internet and it has been nothing but noise and confusion ever since.

What good does knowing this formula do?


Thats pretty funny. My wrists are 5.5 or 6 and my biceps are just over 15". Also, i don’t train biceps.

Let’s go back to the beginning.

When you measured your wrist, did you also measure your bicep? If so, how big was it?


I think that was the measurement for your forearms. What did you input? From what I saw you would be closer to 16 inches.

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Has anyone ever investigated Bicep Curl 10 rep max as an indicator of Bicep Potential?

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How does knowing this information benefit you? How does it change your goals? How does it change your plan?

My flexed bicep measured just under 9.5 inches.

My forearm potential result is 10 inches. Here is what I got.

Stop whatever you are doing and go eat something Right Now!


Hummm… I’d like to see a pic of that flexed bicep.


IDK man, my biceps curl weight has always been shit and I’m toting around some 17.5" pythons.

Solid point though.

Are you measuring your bicep or your elbow?

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That is pretty small. I’m also 5’7 but my wrists are 7”. I have 17” arms but weigh 205lbs. What are your other current stats. Even if you couldn’t get huge arms, a lean arm with nice proportions looks good on a small body.

What calculator is that? The ones I have seen ask for height, wrist, ankle and bw or bf% none give a 12 inch bicep.

I think the most important question hasn’t yet been asked…

Why do you care what this calculator says?

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Here you go. This is fully flexed btw