I have to convert a lot so I just use 1 inch = 2.5 CM (not exact, but close enuff) and easy to remember.
As an Engineer wish the heck we had changed back in the 1970s when it was seriously discussed. Except for gal -->liter. I do NOT want to think of how expensive gasoline is in liters. Nor how fast the the meter spins on the gas pump in liters.
