I purchased two pairs for an upcoming camping trip. I got an XL and an XXL. I tried on the XL and they fit perfectly. Not loose, not tight at all, just right! I got a bigger size too in case I was feeling bloated (I have gastrointestinal problems due to gastric sleeve surgery and losing my gallbladder so sometimes a bigger size is helpful to have on hand).
I wear a size 16 so whatever size you normally wear, I'd say stick to that size.
You really can't beat the price!