Good idea, wtf. Let me take it one step further. (This is a coincidence because I did it tonight for the first time.)
I used a little narrower strip of paper, probably more like 1/4”. Then I measured very carefully ( in my case, to my current goal of 5 1/8”) and cut it to length. Took a little bit of Scotch Tape and very carefully taped the two ends together, abutting one another.
Voila. Ring around the penis. Just put it on and forget it while get yourself hard, then see if you fill it out. It’s really quite accurate if you’re careful when putting it together. You don’t have to tie up one hand, interrupt getting yourself hard, and measurement anxiety is, well, gone.
If you can fill it out, congratulations — now make another one, maybe a 1/16” bigger.
Man, what you could do with a paper cutter. Just don’t get your pride and joy too close.
And yep, I hit the 5 1/8” so now I’m on to bigger and better strips!