Wall area calculator

How to use the wall area calculator

Use this wall area calculator to find the surface area of a room’s walls after subtracting doors and windows. It is useful for estimating paint, wallpaper, paneling, or other wall materials.

1. Choose Feet or Metres under Units.
2. Enter the room length, width, and wall height.
3. Enter the number of Doors and Windows.
4. Review or replace the Area per door and Area per window values.
5. Use the net wall area for material estimates.

What to enter

Units

Choose Feet for imperial measurements or Metres for metric measurements. Results use sq ft or m² accordingly.

Room length

Enter the room length in ft when using Feet, or m when using Metres.

Room width

Enter the room width in ft when using Feet, or m when using Metres.

Wall height

Enter the wall height in ft when using Feet, or m when using Metres.

Doors

Enter the number of doors. Use 0 if the room has no doors.

Windows

Enter the number of windows. Use 0 if the room has no windows.

Area per door

Enter the area of one door in sq ft or m². The default is 21 sq ft, based on a 3 × 7 ft door, or 1.95 m² in metric mode.

Area per window

Enter the area of one window in sq ft or m². The default is 15 sq ft, based on about a 3 × 5 ft window, or 1.4 m² in metric mode.

Example: a 12 ft × 10 ft room

For a room that is 12 ft long, 10 ft wide, and 8 ft high, with 1 door and 2 windows: perimeter = 2 × (12 + 10) = 44 ft. Gross wall area = 44 × 8 = 352 sq ft. Door area = 1 × 21 = 21 sq ft. Window area = 2 × 15 = 30 sq ft. Total opening area = 21 + 30 = 51 sq ft. Net wall area = 352 − 51 = 301 sq ft.

How wall area is calculated

The calculator finds the room perimeter with 2 × (length + width). It multiplies the perimeter by wall height to get gross wall area. It then subtracts the total opening area: doors × area per door + windows × area per window. The result is net wall area. Values are converted between feet and metres when needed and rounded to 2 decimal places.

Reading the results

Gross wall area is the total area of all four walls before openings are removed. Door area and window area show the deductions. Net wall area is the remaining wall surface to use as the starting area for paint, wallpaper, paneling, or similar materials.

Limitations and common mistakes

• The calculator treats all four walls as a rectangle with one consistent height.
• Each door uses the same area, and each window uses the same area. Enter custom average areas or measure openings separately for a more precise estimate.
• Irregular walls, sloped ceilings, alcoves, and partial-height sections are not modeled.
• The calculator does not add a material waste allowance.

Frequently asked questions