Wall Square Footage Calculator
Get the exact wall surface area for paint, wallpaper, tile, paneling, or drywall. Enter a wall's height × length; subtract doors and windows.
Last updated:Tip: If you only have the diameter, divide by 2 to get the radius.
L-shape = two rectangles sharing a corner.
Add one row per rectangle and we'll sum them.
How to Measure Wall Square Footage
- Measure each wall separately — height × length.
- Add the four walls of a room together.
- Subtract openings: a standard door is ~21 sq ft; a standard window is ~15 sq ft.
- Add 10% waste for cuts, trim, and mistakes.
Wall Area Quick Reference
For a typical room with 8 ft ceilings, wall area is roughly perimeter × 8 minus openings.
| Room Size | Perimeter | Wall Area (8 ft ceiling) |
|---|---|---|
| 10 × 10 | 40 ft | 320 sq ft |
| 12 × 12 | 48 ft | 384 sq ft |
| 12 × 15 | 54 ft | 432 sq ft |
| 15 × 20 | 70 ft | 560 sq ft |
| 20 × 25 | 90 ft | 720 sq ft |
Subtract ~20 sq ft for each door and window to get the final paintable or paperable area.
Standard Openings to Subtract
| Opening | Typical size | Area to subtract |
|---|---|---|
| Interior door | 32 × 80 in | ~21 sq ft |
| Entry door | 36 × 84 in | ~24 sq ft |
| Double-hung window | 36 × 60 in | ~15 sq ft |
| Picture window | 60 × 60 in | ~25 sq ft |
| Sliding patio door | 72 × 80 in | ~40 sq ft |
| Garage door (single) | 96 × 84 in | ~56 sq ft |
Vaulted and Cathedral Ceilings
For a sloped wall, compute the rectangle below the slope plus the triangle above. For a gable wall that is 12 ft wide with an 8 ft wall height and a peak 4 ft above:
- Rectangle area: 12 × 8 = 96 sq ft
- Triangle area: (12 × 4) / 2 = 24 sq ft
- Total wall: 120 sq ft
Use the triangle calculator to double-check the slope section.
Wallpaper and Tile Orders
Wallpaper is priced per single roll (~28 sq ft) or double roll (~56 sq ft). Divide the wall area by 25 to allow for pattern match and cuts. For a tile accent wall, use the tile calculator; most wall tile layouts need a 10–15% waste factor.
Frequently Asked Questions
How do I calculate the square footage of a wall?
Multiply the wall height by the wall length in feet. An 8 × 12 ft wall is 96 sq ft. Subtract about 21 sq ft for each standard door and 15 sq ft for each window.
How do I calculate total wall area for a room?
Add the lengths of all four walls (that is the perimeter), multiply by the ceiling height, and subtract the area of each door and window.
Do I count the ceiling in wall square footage?
No, unless you are also painting or papering the ceiling. Wall square footage is vertical surface area only.
What wall area should I subtract for a standard door?
About 21 sq ft for a 32 × 80 inch interior door. Subtract 24 sq ft for a 36 × 84 inch front door, and 40 sq ft for a typical sliding patio door.
What wall area should I subtract for a standard window?
About 15 sq ft for a 36 × 60 inch double-hung. Large picture windows can be 25 sq ft or more — measure each one because they vary a lot.
How much wallpaper do I need per wall?
Most standard US wallpaper rolls cover about 28 sq ft per single roll. Divide the total wall area by 25 to leave room for pattern match and cuts.
How do I measure a wall with vaulted or sloped ceilings?
Treat each slope as a triangle: base × height / 2. Add the triangular areas to the rectangular portions below to get the total wall square footage.