How to measure a room for flooring, paint, and tile
Almost every material calculator starts with one number: square footage. Get that right and the rest is easy. Here's how to measure it correctly for floors, walls, and the awkward rooms that aren't simple rectangles.
Floor area vs. wall area
The first thing to settle is which surface you're buying material for, because it changes what you measure:
- Flooring and floor tile use the floor area — length times width of the floor.
- Paint and wall tile use the wall area — the perimeter of the room times the ceiling height.
They're different numbers for the same room, so don't measure once and reuse it for both.
Measuring floor area (for flooring and tile)
For a simple rectangular room, measure the length and width in feet and
multiply: a 12 ft by 15 ft room is 12 × 15 = 180 square feet.
Measure to the wall, not the baseboard, and round each measurement up to the nearest
few inches rather than down.
Odd-shaped rooms
An L-shaped room, a bump-out, or a closet alcove is just rectangles in disguise. Split the floor into rectangles, calculate each one's area, and add them together. For a closet or doorway you'll actually floor, include it; for a kitchen island or built-in you won't, subtract its footprint.
Measuring wall area (for paint)
For paint, add up the length of every wall to get the room's perimeter,
then multiply by the ceiling height. A 12 ft by 15 ft room with
8 ft ceilings has a perimeter of 2 × (12 + 15) = 54 ft, so the wall
area is 54 × 8 = 432 square feet. Subtract roughly 20 sq ft per
door and 15 sq ft per average window. Don't forget the ceiling if you're painting it.
Turn your measurements into a shopping list
Once you have the square footage, plug it into the matching calculator and it will handle the coverage rates, box sizes, coats, and waste for you: