Wall Square Footage Calculator
Enter your room size and ceiling height to get the wall area — both the gross figure and the paintable figure after doors and windows come off. Add the ceiling if you are drywalling or painting it too.
Results
How wall square footage works
Wall area is the perimeter of the room multiplied by the ceiling height. The perimeter is what matters, not the floor area — a long narrow room and a square room can have identical floor space and quite different wall space.
Formula: 2 × (length + width) × height = gross wall area, then − (doors × 21) − (windows × 15) = paintable area
A 14 × 12 ft room with 8 ft ceilings has a 52 ft perimeter and 416 sq ft of gross wall. Take off one door and two windows and 365 sq ft is left to cover. That second number is the one that decides how much paint, wallpaper or drywall you buy.
| Opening | Typical size | Area deducted |
|---|---|---|
| Interior door | 30–36" × 80" | ≈ 21 sq ft |
| Exterior door | 36" × 80" | ≈ 21 sq ft |
| Standard window | 36" × 60" | ≈ 15 sq ft |
| Large or picture window | 60" × 60" | ≈ 25 sq ft |
| Sliding patio door | 72" × 80" | ≈ 40 sq ft |
If your openings are much bigger than the standard sizes — a wall of glass, a wide cased opening between rooms — measure them and use the wall-length mode with a reduced run, or subtract the difference by hand.
When to deduct openings, and when not to bother
Trade practice splits here, and both sides are defensible:
- Painting a normal room: most painters ignore one or two ordinary windows and buy to the gross figure. Paint is sold in whole gallons, the deduction rarely changes the count, and the surplus covers a second coat on the patchy wall.
- Drywall and wallpaper: deduct. Sheets and rolls are bought in whole units and the offcuts around an opening are usable elsewhere, so the deduction is real money.
- Large openings: always deduct. A patio slider is 40 sq ft — more than a tenth of a typical room's walls, and enough to move you down a paint size.
- Quoting a job: deduct, and say so. A quote built on gross area looks padded next to one built on net.
Wall height is the number people get wrong
Eight feet is the default here because it is the most common ceiling height in American homes, but it is worth checking rather than assuming. Nine and ten foot ceilings are standard in newer construction and add 12–25% to every wall in the house. Rooms with a vaulted or sloped ceiling need the average height, not the peak — measure at the low wall and the high wall and take the midpoint, which is exact for a straight slope.
Measure to the top of the baseboard rather than the floor if you are papering or painting the walls only. Over a whole room a 4-inch baseboard is worth around 17 sq ft on a 52 ft perimeter, which is most of a window.
Frequently asked questions
How do I calculate the square footage of a wall?
Multiply the wall length by the ceiling height. For a whole room, add the four wall lengths together — that is the perimeter, or 2 × (length + width) — and multiply that by the height. A 14 × 12 ft room with 8 ft ceilings has 416 square feet of wall before openings.
Do I subtract windows and doors when calculating paint?
For one or two ordinary windows, most painters do not bother: paint comes in whole gallons and the deduction seldom changes how many you buy. Subtract when the openings are large — a patio slider takes off about 40 square feet — or when you are estimating drywall or wallpaper, which are bought in whole sheets and rolls.
How many square feet of wall is a 12x14 room?
The perimeter is 2 × (14 + 12) = 52 feet. With an 8 foot ceiling that is 416 square feet of gross wall. After one door (21 sq ft) and two windows (15 sq ft each) it comes to 365 square feet of paintable wall.
What is the standard wall height for calculations?
Eight feet is the most common ceiling height in US homes and is the default on this calculator. Newer construction often uses 9 or 10 feet, which adds 12–25% to the wall area, so measure rather than assume. For a sloped ceiling, use the average of the low and high wall heights.
How do I calculate wall area for an irregular room?
Switch the calculator to total wall length and add up each wall individually with a tape measure. That handles bays, alcoves and any room that is not a plain rectangle, since it never assumes the room has four walls at right angles.