Anyone know how to determine the size of pants? (No tag)

MBrothers22

So I'm at that point to where I need to start looking for new pants. I started at a tight 46 inch waist and I'm in desperate need for smaller pants. I went to a thrift shop and got some pants that were a little snug but wearable. Only thing is they don't have any tags on them. My initial thought was they were 44s but after measuring them I'm not so sure. Zipped up and buttoned, they measured 20 inches across. I also measured 3 of my 46 inch pants and they were 23 1/2 inches, 24 inches, and 24 1/2 inches across. This is measuring straight across the waist band.

I'm pretty much just asking this out of curiosity because I may be down 2 pant sizes when I thought it was just one