It's probably not the same scale (although we could pretend), in Dungeons and Dragons: Warriors of the Eternal Sun, whenever your characters rest in the wilderness to get their HP back, 2 seconds (roughly) equals an hour. You theoretically could calculate how far a person could walk in an hour, find out how long it takes to walk from one point all the way back to the same place, and calculate roughly how big the planet is. Okay, that may seem silly.
I've always wondered what the diamter of the sections of the Alisa III is.