A digital caliper is a great tool to have around for all kinds of measurements. An example of how I use the caliper: When I want to use LEDs in one of my projects, I like to find a drill bit just a little smaller than the LED without drilling a bunch of trial and error holes. That way the LED will be a nice pressure-fit in the hole and won’t need to be glued into a hole that is oversized.
Here are some at Amazon: http://amzn.to/2BR4MZ0