When my American friends insist that feet and inches is just easier for them, I just nod in agreement and give them measurements using rods, chains and furlongs as well. If you’re going to go Imperial, you have to know 'em all. An acre is a chain by a furlong, totally logical as that would be 4x40 rods which is of course 43560 square feet. I guess it makes complete sense when your world is only a few furlongs across.