Smart Build Calculators

Wall Area Calculator

Get the wall area of a room with doors and windows deducted. This is the number that paint, wallpaper, plaster and putty calculators all build on.

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Formula and method

Gross wall area is twice the sum of length times height and width times height. Openings are calculated from door and window counts and sizes and subtracted to give the net area.

How to measure the inputs

  1. Measure room length and width, then measure floor to ceiling height.
  2. Count doors and windows and measure each width and height.
  3. Note the result — you can reuse it in the paint, wallpaper and plaster calculators.

Worked example

Room length 13.12 ft; Room width 9.84 ft; Room height 8.53 ft; Door count 1; Door width 2.62 ft; Door height 6.56 ft; Window count 1; Window width 3.28 ft; Window height 3.28 ft → Net wall area: 363.82 ft²

Practical tips

  • Sketch the room and write each measurement on the drawing.
  • Measure both ends of every wall: lengths usually differ slightly.
  • Keep the perimeter for skirting board ordering.