How to measure a room for paint
A plain way to measure walls, subtract doors and windows, and avoid buying the wrong amount of paint.
Paint estimates start with wall area. You do not need perfect drafting skills. You need a tape measure, wall height, room length, room width, and a rough count of doors and windows.
1. Measure the room perimeter
For a simple rectangular room, measure the length and width. Add them together, then double it.
Example: a 12 ft by 10 ft room has a perimeter of 44 ft.
2. Multiply by wall height
Most rooms have 8 ft walls, but do not guess if the ceiling looks taller. Perimeter times wall height gives the rough wall area.
Example: 44 ft perimeter x 8 ft high = 352 sq ft of wall area.
3. Subtract doors and windows
You can measure every opening, but a quick planning estimate usually subtracts about 20 sq ft per door and 15 sq ft per window.
If your windows are large or the room has a big opening, measure those separately.
4. Decide on coats
Two coats is a safe default for many repainting jobs. One coat may work for touch-ups with the same color. Dark-to-light changes, stained walls, repairs, and strong colors can need primer or extra paint.
5. Check the can
Paint coverage varies. Many cans list something around 250 to 400 sq ft per gallon. Use the number printed on the product if you already know what you are buying.
If you are changing from a dark color to a light one, price primer before you buy extra finish paint. Primer is often the cheaper fix.