Ideal top tube length for BMX Regarding BMX bikes, is there an easy way to determine what top tube length is most suitable for a person based on their height? In my experience, most LBS only want to talk about BMX size in terms of wheels ("it's a 20 inch" or "it's an 18 inch) since they're mostly considered to be kid's bikes.

This is the tool you're looking for:

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It's not a linear calculation, but it would be fair to say that a rough estimate is: start with a 22.5" top tube for a 6' adult male, and add/subtract half an inch of top tube for every inch of height. ![bmx calculator](