How many square feet in a 10x10 with 8ft ceilings?

10' by 10' with 8-ft ceilings:

-- Floor = 100 square feet

-- Ceiling = 100 square feet

-- Each wall = 80 square feet

Total interior surface area of the room = (2 x 100) + (4 x 80) = 520 square feet.

(Less Windows, recessed light fixtures, doors, electrical outlets, etc.)