Easiest and most reliable way to measure ERD?

I’ve read a number of different ways to do this on the net but want to know how most of you do it.

Actually forget ‘easiest’ and give me most reliable please

Entity Relationship Diagram?
It must be a new young persons thing?

more reliable is to just use the manufacturers ERD or what’s listed on spocalc or dt swiss if its a bit older. but if you want to double check…

you need 2 spokes, 2 nipples, a tape measure or some sort of accurate measuring device

put the spokes in opposite holes, measure the combined spoke length to the start of the nipples

then add 2x the length of a nipple you used and there is your ERD

worth noting that some people measure to the end of the nipple, some measure to where the nipple/rim interface is