# How do I measure handlebar diameter?



## coopdad (Nov 6, 2010)

My son's new bike is a little big for him so I am going to get a shorter stem. The problem is I am not sure how do I measure handlebar diameter. 
thanks!


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## DennisF (Nov 4, 2011)

If there is a bulge where the stem attaches, 31.8mm. Otherwise, 25.4mm.

http://www.bikeman.com/bicycle-repair-tech-info/bikeman-tech-info/1637-handlebar-diameters

If you get by a Harbor Freight store, pick up one of their cheap digital calipers. I got mine on sale for $10.

Another idea: tighten an adjustable wrench on the bar, then measure the distance between the jaws with a ruler.


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## Lone Rager (Dec 13, 2013)

I saw some dial calipers at Loews or maybe Home Depot for ~$18. Amazon has all sorts of digital and dial calipers with digital being cheaper and starting ~$12. A handy instrument to have in your toolbox.


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## Joules (Oct 12, 2005)

Just use a ruler or tape. The bar is either 1 1/4" (aka 31.8) or 1" (25.4), you can eyeball close enough. 

Or remove the bar from the stem, many stems have dimensions printed on the inside of the clamp. You could also measure the clamp; might be easier than measuring the bar directly.


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## DennisF (Nov 4, 2011)

> You could also measure the clamp; might be easier than measuring the bar directly.


Glad someone is using his head


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## coopdad (Nov 6, 2010)

Thanks so much everyone!


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