Whats the compression rating on them

"20-30mm/Hg" This means it provides 20-30 "millimeters of mercury", which is the measurement for pressure. The compression is highest at the feet and gradually decreases up toward your knee. This ensures your blood or extracellular fluid travels up your leg toward your heart.

These are the thinnest compression stockings I have ever worn. They are also the coolest ones that I've ever worn. Definitely not thick one bit.

I wear a size 8 in womens shoes but have large calfs, 16 inches. I don't know what size to get. ?

You should order by your ankle size because they are supposed to squeeze theankle & calf to keep the leg from swelling. I wear a size 8 shoe & have large calfs, but my ankle is 6 inches & I wear a S/Med.

Men's shoe size 12-12 1/2, calf diameter 22". Will the XL fit without being too tight?

I wear a similar size shoe and have a smaller calf. But, I ordered the XXL by accident. And though it is loose in the beginning, after washing they tend to tighten up. So I find that the XXL is a best option for anyone wearing size 12 or larger. Just my two cents.