Wall Area Calculator

Gross and net wall area in square feet or square metres — for a single wall or a whole room — with door and window deductions. Use the net area for paint, drywall, wallpaper or tile take-offs.

Dimensions

Mode
ft
ft
ft
8 ft (2.44 m) standard residential.

Openings

ft²
Standard 32″ × 80″ door ≈ 21 ft² with frame.
ft²
Typical 3 × 4 ft residential window ≈ 15 ft².

Calculation results

Net wall area

— ft²

Gross wall area

— ft²

Total deductions

— ft²

Wall perimeter

— ft

Net area = gross area − deductions. Use this for paint, wallpaper or tile take-offs. For drywall sheet count include the ceiling area too (drywall deducts only 20 ft² per door — slightly less than paint).

Informational only. Door and window areas assume standard residential sizes. For oversized openings (sliders, garage doors, picture windows), enter the actual area in the override fields.

Understanding the formula

Single wall

gross = length × height  ·  net = gross − openings

Room (four walls)

gross = 2 × (length + width) × height

The 2 × (L + W) part is the room perimeter — sum the four walls. Multiplied by ceiling height it gives the total vertical surface. Add the ceiling (L × W) if you also need to paint or finish overhead.

Worked example — 12 × 10 ft room, 9 ft ceiling, 1 door, 2 windows

  • Wall perimeter = 2 × (12 + 10) = 44 ft
  • Gross walls = 44 × 9 = 396 ft²
  • Deductions = 1 × 21 + 2 × 15 = 51 ft²
  • Net walls = 396 − 51 = 345 ft²
  • Ceiling area = 12 × 10 = 120 ft²

Frequently asked questions

How do I calculate the area of a wall?
For a single wall, multiply length × height. For a room, take 2 × (length + width) × ceiling height — that adds up all four walls. Subtract standard door area (21 ft²) and window area (15 ft²) for each opening to get the net paintable or sheathable area.
What is the standard area of a door for paint estimating?
A standard 32-inch × 80-inch interior door has a clear opening of about 17.8 ft², or roughly 21 ft² including the frame and casing. Some calculators use 20 ft² for drywall (because the casing is covered separately) — either is acceptable.
What is the standard window area?
15 ft² is the conventional default — it represents a typical 3 ft × 4 ft (36" × 48") double-hung window with frame. For picture windows, sliders or oversized casement windows, measure and override.
Should I include the ceiling in wall area?
No — wall area and ceiling area are separate measurements. Add them only if you are painting or finishing both. The calculator separates them so you can use whichever applies.
How much wall area in a 12×12 room?
A 12 × 12 ft room with 8 ft ceilings has a gross wall area of 2 × (12+12) × 8 = 384 ft². With one door and two windows deducted: 384 − 51 = 333 ft² net wall area.
What is the wall area of a 10×12 bedroom?
At 8 ft ceiling: gross = 2 × (10+12) × 8 = 352 ft². With one door and one window: 352 − 21 − 15 = 316 ft² net wall area. At 9 ft ceiling: gross = 396 ft², net = 360 ft².