Wall Square Footage Calculator
Wall square footage is length × height for each wall, added together, minus doors and windows. A 20 ft wall and a 12 ft wall, both 8 ft high, total 256 ft²; less 36 ft² for a door and a window, that is 220 ft² of net wall. Use it in the Paint Calculator or the drywall and wallpaper tools.
How it's calculated: Net area = (length × height) + (second length × height) − doors and windows.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Area = (Length × Width) + (second Length × second Width) − openings
Run the calculation to see each step with your own numbers.
A 20 ft wall 8 ft high, plus a 12 ft wall 8 ft high, with one door and one window.
Wall 1 = 160 ft²; Wall 2 = 96 ft²
Less 36 ft² openings → 220 ft²
- Rectangular areas. For a room with more than two rectangles, or angled walls, split it and total the parts.
- The result is a net area — feed it into a material calculator, which adds its own waste allowance.
- Should I subtract every window?
- For paint and wallpaper, deducting openings over about 10 ft² is worth it; small windows are covered by the waste allowance on the material calculator. For an exact drywall or panel take-off, deduct them all.
- Do I include the ceiling?
- No — this is wall area only. Add the ceiling separately (length × width) if you are painting or drywalling it too.
- How do I handle a gable or sloped wall?
- Split it into the rectangle below the slope plus the triangle above. A triangle's area is half its base times its height — add that as the second area, or work it out separately and total.
- How do you calculate the square footage of a wall?
- Multiply the wall's length by its height, add any other walls the same way, and subtract doors and windows. A standard interior door is about 21 ft² and a typical window about 15 ft².
- How many square feet is a 12 × 8 wall?
- 96 ft² before openings: 12 ft × 8 ft. Deduct about 21 ft² for a standard door or 15 ft² for a typical window if the wall has one.
Geometry
Standard geometry (sum of rectangles). Unit conversions per NIST SP 811.
About the Wall Square Footage Calculator
The Wall Square Footage Calculator gives the surface area of one or two walls with doors and windows deducted — the paintable, paperable or boardable area. Feed the result into the Paint, Wallpaper, Drywall or Shiplap calculators, which add their own waste. A standard interior door is about 21 ft² and a typical window about 15 ft²; deduct the real sizes if yours differ a lot.
What you enter
- Length
- Width
- Second area — length — Add an L-shaped extension. Leave 0 if not needed.
- Second area — width
- Doors & windows — Total area of openings. A standard door is ~21 ft²; a typical window ~15 ft².
What you get back
- Wall Square Footage — the exact result of the calculation.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Wallpaper Calculator — Wallpaper rolls for a room from wall area and pattern repeat.
- Wall Paint Calculator — Paint for walls only, with doors and windows deducted.
- Drywall Calculator — Drywall sheets, screws, mud and tape for a room.
- Shiplap Calculator — Shiplap boards and lineal feet for a wall area.
Part of the Walls calculators.