To correctly measure you foot you will need assistance of another person. Standing (not sitting) place your foot on a piece of paper and have someone trace around your food with No 2 Pencil. Take the tracing and a ruller and draw the longest line possible within the boundaries of the tracing. Measure it in inches to the closest 16th of an inch and plug it into this chart. Once you get a size please add 1  to it and this will be your skate size. 

As a general rule of thumb, your US Woman shoe size should equal to the Riedell size. For men - take your US shoe size, add 1.5 sizes to it and that will be your Riedell size.

VERY IMPORTAN INFORMATION ABOUT FITTING SKATES PLEASE READ

When trying on skates please don't forget to lace the skates on your feet completely as if you were to go skating. This is because when the skates are new the heel part of the skates is very tight and your foot wont slide all the way back.