How did you work out the right breast pump flange size?

[MomSolutions]

I’m curious how everyone worked out their breast pump flange size. Did you measure before buying your pump, or did you have to try a couple of sizes before finding one that felt right?
I keep seeing different sizes mentioned and wasn’t sure whether the standard size that comes with a pump works for most people.

My pumps had a piece of cardboard with holes in it which had different diameters. You're meant to put your nipple into each hole and find one which is just a tiny bit loose around the nipple. I'm sure you can order this measuring tool somewhere or even make it at home - draw a line half as long as the diameter, draw a circle with a drawing compass and cut it out to make a hole