Want to fit your bike based on bone structure? You could head down to your local professional fitter, which as Eddie at 55nine likes to remind me is the best way to do it since they’ll take pedaling mechanics, flexibility, equipment and other such things into consideration. Or, you can get the Size My Bike app for iPhone, iPod Touch or iPad.
Size My Bike claims to take six body measurements (height, inseam, shoulder width, sternum, and arm and foot length) into account, then computes the optimal size frame and fit measurements. They say its good for taking to a bike shop to get the right size bicycle, and for getting it to fit correctly once you’ve brought it home. There are settings for both road and mountain bikes.