There are plenty of ways to size a bike frame to yourself. Notice I said 'size a bike frame to you', not the other way around. When you purchase a bike, the bike should be custom fitted to you, not the other way around. One of the best websites I've seen on how to fit a bike frame to you, is the Fit Calculator on Competitive Cyclist website: www.competitivecyclist.com
You'll need a tape measure, stool, a bubble level and someone to take the measurements.
You'll need to take 8 measurements. What's nice about the Competitive Cyclist Fit Calculator is that is shows you how to correctly take the measurements with both a photo and a video. It doesn't get any easier/better than that. You can take your measurements in either inches or centimeters. I'd take it in inches since most tape measures are in inches.
Here are the 8 measurements you need to take (I've included my measurements):
Lower Leg- 23"
Sternal Notch- 58"
Total Height- 71"
After taking my measurements, I entered them into Competitive Cyclists Fit Calculator. Competitive Cyclist gave me 3 different results (for 3 different fits): a Competitive Fit (for aggressive riders or racers looking for speed over comfort), an Eddy Fit (less saddle to handlebar drop for more comfort), and the French Fit (puts you in a more upright riding position for maximum comfort and the largest frame). Out of curiosity, I included the measurements from my Trek Madone 5.2 road bike (which is the same bike Lance Armstrong used to ride- so it's a race bike). I was dumbfounded by the results. It seems like my Trek Madone is a combination of all 3 fits..ha. (see yellow highlights) Go figure.
BTW, Trek recommends frame sizing from height alone. According to the Trek sizing chart, I could ride either a 56cm or a 58cm size frame. Since I'm 5'11" tall, I'm in the middle. Too bad they don't sell a 57cm size frame. I believe I opted for the 58cm size frame. Perhaps that's why my bike measurements span all three of Competitive Cyclists Fits. Now I'm wondering if my seat/saddle height is a little too low (BB Saddle position). That would definitely put me in a more aero position when I'm in the drops. Also seems like I can move my seat up a tad, which would decrease my saddle setback. I'm not doing anything right now, because I'm comfortable when I ride and seem to be producing optimum power...for an old guy.
Power ON! Coach Rob