You aren't going to duplicate on the trainer what you encounter on the road. Just use the crank length that feels good to you and don't worry about what a calculator says. They are often based on someone's own idea of what is ideal.
Crank length isn't so much just upper and lower leg length. Other things like your actual range of motion you have and what you consider a comfortable rpm at any particular power output matter too. It's very much a personal thing.
I like shorter cranks than my 34.5" inseam suggests. 165mm to be exact. I also tend to like a higher cadence.
Last edited by Iride01; 04-29-22 at 12:24 PM.