Are you trying to fit someone else on a bike? Or are you fitting yourself using books/online resources as a reference?
If you are trying to get yourself fit on a bike, I would only trust the fitting from the LBS. They have the advantage of seeing things that you don't .. and of course they have the experience of doing many fittings.
If you're trying to fit someone else on a bike.. I would recommend having them sign a waiver.
Sounds like good advice, as a bad fit can cause injury.
You'll find big differences in getting a fit by a program because of many reasons: Different styles of fit, such as racing, touring, sport, etc. You'll also get someone who figures that what's good for them is a great yardstick for everyone else. (it's like, hey, I like this Nike running shoe, so it'll work perfrct for everyone else in their size)
If you look at competitive cyclist's fit calculator, you'll see three different fit recommendations, which will put you into different positions and even different size bikes. By their calculator, I'm riding a bike too big for me. However, when I did have a bike of the recommended size, I had a lot of back pains which I don't now.
If you're trying to measure yourself you're likely getting a large margin of error. 2nd, some of the well know fit setup out there don't use or do place a high importance on foot size, which can impact saddle height in a big way.
Also, a word on size. Size is bunk. Buy a bike based on stack and reach. There is only one way to measure each of those. I ride a 54 in one manufacturer, 53 in anotherm and a 57 in another. All have a stack an reach within a few mm and are thus almost idnetical in size.
All good advice. You don't say specifically what your point of references are, but no matter, the best online sources will get you is in a range for fit, and that IMO is pretty near useless. A reputable LBS can do better in 1/2 hour, so as others have offered get to one and get fit correctly.
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