You can just say you don’t know fractions.

It’s okay.

They used to give out a little conversion rotary slide rule at trade shows. Pretty nice tech, two circles of cardboard pop riveted together in the center, on the top one the units are written on a series of rings, smallest on the outside, biggest on the inside, there’s a cutout along the radius so you can see the numbers written on the bottom one. Spin the bottom one so the unit you know is showing and the one you want will be right there.

I bet they still make em.