"Plain English" for cloth shin pad sizing:
For sizing on shin pads, it’s not something like your shoe size or height that defines your shin pad size.
Since they are elastic AND they don’t cover your toes, the size of your foot isn’t the biggest issue. It’s more about a comfortable fit for your calves and how much bulk you want on your shins.
The diameter of your leg is really the most important thing. We recommend that you use your t-shirt size as a guide. That works pretty well (unless you're REALLY tall and skinny or, ahem, "Big Boned"). That's what we have them made to fit.
So it generally ends up corresponding to your t-shirt size.
Another way to gauge it: if you wear a size 2 or 3 gi , you’ll usually wear a small shin pad, 3 or 4 gi is a medium, 5 or 6 is a large, 6 and up is usually an X-Large shin pad. We do have XX-Large in some styles if you think you'll need them.
Keep in mind that since they ARE elastic, they will accommodate a range of calf diameters.
The shin PAD length for each size is roughly:
X-Small: 8 ½”
Small: 9 ½”
Medium: 10 ½“
Large: 11 ¾“
X-Large: 12 ¼”
XX-Large: 13 ¼”
So the bigger the size, the more shin it covers.