There are all kinds of ways for measuring fit. Everyone has different dimensions, its not just based on height, nor is it based on inseem. So...if the current bike you have seems to be comfortable-tune it up+ride it, but take it easy. A poorly fit bike can cause you serious injury, particularly if you "ride hard", or long (repetitive stress injuries). At the same time, a poorly fit bike can be ridden-and simple adjustments made to make the fit better (seatpost/saddle height, seat/saddle setback, handlbar height). Also, most bike measurements are done with the metric system (excluding "stand over" height-which is usually measured in inches).


Click here for a rather nice article regarding bicycle fit written by Peter White. This is but just one of many available for free on the web. Some even have calculators, where you enter specific bone lengths etc. But this particular article is a great starting point. FYI: Most shops will charge for a "fit", especially if you are not purchasing a bike.