[JimiofEden]

I mean, the basic rule of thumb I learned for C was that 20 is room temperature, above 30 is hot, below 0 is freezing

Same deal with F, 70 is room temperature, above 90 is hot and below 30 is freezing

That alone has been enough to help me switch back and forth between the two systems easily enough. Or at least I'm not shocked when 14 C is kinda chilly or when 95 F is damn hot

Granted, if you need to be more precise than that, then that comes down to having a calculator handy, but for common use this has been enough for me

Edit: In hindsight, this might just mean that as a F native, C is much easier to learn than the other way around