Converting frame size to wheel size I've been trying to determine what size road or mountain bike I should purchase. All the charts I've found suggest what frame size I should have, but online shopping only lists wheel sizes. How do I determine what wheel size is best for my height?
Generally, there are a few wheel sizes for adults on the market now:


700c: This is the standard adult road bike wheel size. For mountain bikes, this is often sold as 29" and is also the standard (where they're said to roll over bumps easier than a 26" but at the cost of manuverability and weight). The rim diameter is 622 milimeters. 
650b: This is becoming more popular with shorter riders for road and mountain biking (where its often sold as 27.5", as a compromise between 26" and 29"). It is smaller than 700c with a rim diameter of 584 millimeters. 


Less commonly, you'll find:


26": This was the old standard size for mountain bikes. The rim diameter is 559 mm. 


All these wheel sizes are available for a wide range of frame sizes (usually reported as some number of inches or centimeters, e.g. 58cm for a road bike or 23" for a mountain bike, or small/medium/large/etc.). My guess is that you're reading the frame size and thinking it is the wheel size. 

Note that frame sizes are not standardized between bike models or even related models (e.g. a bike that is sold in both a 26" and 700c wheel version), so you need to try the bikes to see if they fit you well, and/or compare their geometries (e.g. standover height, top tube length, etc.). 

Useful links on tire sizing: Rivendell
Useful links on bike sizing: Sheldon Brown