I now own three pairs! As I'm a tall (5'10" with inseam of 33" ) average build senior, I first bought an XL tall, which turned out to be too long and too big. I didn't care. They arrived in the middle of the winter and, soft and warm, I wore them constantly. Under a dress or tunic I just had to periodically hitch them up but could hide their excess length by wearing a pair of boots. I also wore them under another pair of pants. These keep a senior lady who feels chilled 9 months of the year comfortably warm.
Then bought a pair in purple on sale (!) in a L regular and while on the site ordered another pair in black in L regular. THEY FIT PERFECTLY.
I'm keeping the XL tall ... I'm going to pull out my sewing machine and sewing box and make some alterations to them.