Changed my avatar to one of my paintings. This tool would be a great time saver.
Would love to have one.

I am also a graphic designer and have used a proportion wheel for years. I still use it all the time for all sorts of purposes.

After you have found your first percentage, there is no need to calculate anything if you are still working with the same percentage. Just don't turn the wheels anymore. Tape them together if you have to. All the number pairs (top and bottom wheel) will remain at the same percentage. So to find your next size, look for the number on the original wheel and the reproduction size is right there beneath it on the reproduction wheel.

I love this tool. It is small, portable, works every time and doesn't need batteries.