You can find different shoe width scales on the market. If you are unsure if a particular brand's pair of shoes will fit you properly, check how amazon.
Again, if you don't mind the jitters and all that jazz, it may be worth your time to check out the LipoVida brand.
Otherwise, Pure GCE gets my vote. Good product except the product isn't the best. I've tried a few different brands and this isn't the worst but it's not the best.
Centimeters, shoe size. The following length units are commonly used today to define shoe-size systems: Barleycorn, Paris point, Millimetre, Centimetre (cm). Because the foot is three-dimensional, any two-dimensional measuring tool, such as a ruler or Brannock device®, can only approximate your true shoe size. Please also keep in mind the manufacturers use different lasts to construct their shoes, and sizing may vary accordingly. Match the measurement to the charts below and select your U.S. shoe size it's that simple. Hint: The best ways to measure your foot is to make sure you are standing, wearing the type of socks you will typically wear with your new shoes.