Use a gear range calculator - https://www.sheldonbrown.com/gear-calc.html You only have a couple of entries, the tire size, the crank length, and the size of the chainring and rear gear. It makes comparison simple.
I never did understand the allure of a one speed bike having progressed from that as my first bike to a current 30 gear (some overlap) bike. I really mostly use only the middle chainring and the 10 gears on the cassette but it saves my knees from undue stress.