Measuring your bike with your arm.

[Big T]

I find that if you sit on the bike with your hands on the brake levers and look down, if your front hub is obscured by the bars, then the reach is about right. If the hub's in front of the bars, then the reach is too short, if it's behind, then it's too long.

 

[Paulus]

I would agree that the method of elbow against the saddle and hand on the bars is a good marker to start to get the saddle position and stem length correct for your arm/body length. If the rider can get the saddle position correct, with leg position on the peddles right first, then you can sort out the reach issue. This may or may not include changing the stem for a longer or shorter one as needed. By the way, I always set my bikes up using the arm and hand method and it works for me. My Condor which was built for my measurements also conforms to the arm and hand method

 

[Steve Austin]

all my bikes have been the same size and correct measurement. elbow to fingertips+saddle to stembolt. width of hand =stem length
guess i just fit that model