I guess you can tell we go through a lot of mixing cups in our shop. I may have posted this before but I thought it's worth mentioning again.
No matter what size cups we are using (pints, quarts or 2.5 quart cups) we almost always look at the mixing ratio of the paint products we're using, compute how much we'll need then mark the cup with a Sharpie before we start mixing. It's real easy to screw up a mixture if the cup isn't marked.
As the picture shows, it only take a few seconds to mark the cup but it could save you the $$$ that a small but easy mistake could cost. If the cup is not marked it's very easy to pour paint using the wrong scale or up to the incorrect mark.
Mixing Cup Link