Two Mat Area
The amount of dirt you need to get some peace is a two mat area. Two tatami mats, that is. Also called a tsubo, this is a pretty common measurement in Japan, so you should get really familiar with the amount of space that two tatami mats take up together.
A two mat area also happens to be big enough to hold two bodies (つぼ). That's enough space to bring peace to two living, or dead, bodies!