I'm 5'6" and ride a 54. As others have said - we are all built differently. Test ride as many bikes as you can and a couple of different sizes of the same bike. I was test riding 50/51s of 2 bikes that I had narrowed my choices to and still didn't feel quite right. We tried a 54 and walla - it fit! Now - a 54 on other makes of bike - not good. The geometries can really vary, especially if you're looking at WSD and unisex bikes. Good luck!