How to measure walls for paint

Step by step

1. Go around the room wall by wall

   Note each wall on its own line: its length along the floor and its height from floor to ceiling. Two walls of the same size each get their own line, so none is missed.

2. Measure the doors and windows

   For each opening that does not get painted, multiply its width by its height: a 3 x 7 ft door is 21 sq ft. Add them up per wall: those are the wall's deductions.

3. Choose the coats

   Count the primer coats and paint coats the job needs. The template starts at 1 primer coat and 2 paint coats; change them to fit the surface.

4. Read the spread rate on the can

   The can says how many square feet one gallon covers. The template starts at 375 sq ft per gallon (9.2 m² per liter); use your product's number.

5. Work out the gallons

   The area to cover counts every coat, primer included; the gallons are for the paint coats, added up for all the walls, then rounded up to the next gallon.

The calculation

Net area = length x height, minus deductions. Area to cover = net area x (primer coats + paint coats). Gallons = net area x paint coats / spread rate, rounded up. By default, as in the template: 1 primer coat, 2 paint coats, 375 sq ft per gallon (9.2 m² per liter).

Common mistakes

• Leaving out a wall hidden behind furniture or an open door.
• Forgetting the doors and windows, or measuring them in inches and adding them as feet.
• Using the spread rate of another product: read it on the can you will buy.
• Rounding each wall up instead of the total: add the walls, then round up the gallons.