@odf:

I missed it before when you asked about the default units in LW. It depends on what you set it to in the options, but it uses a grid, and one grid unit will always be one of whatever your default unit is set to.
So if I set it to meters, one grid unit will be one meter square, if I set it to feet, one grid unit will be one foot square and so on.
You can't see the grid units in my screen grabs because I usually turn those on or off, depending on what I'm doing.