Wall Area Calculator
Calculate gross and net wall area with the formula, a worked room example, limitations and related measuring guidance.
Use this before a coating or wall-finish estimate. It shows gross wall area, opening deductions and net wall area. Enter all dimensions in feet.
Measure actual openings where accuracy matters. Whether small openings should be deducted depends on how you are using the estimate and on product/application waste.
How the wall-area calculation works
Gross wall area = 2 × (room length + room width) × wall height. Net wall area = gross wall area − measured door area − measured window area.
Worked example
For a 12 ft × 10 ft room with 8 ft walls, gross wall area is 2 × (12 + 10) × 8 = 352 sq ft. If doors total 18 sq ft and windows total 24 sq ft, the net wall area is 310 sq ft.
When this result is useful
Use net wall area as a starting point for estimating coatings, wall coverings or other finishes where opening deductions are useful.
Important limitations
This tool assumes four vertical rectangular walls. It does not automatically account for sloped ceilings, alcoves, partial-height walls, curved walls, cabinets or surface texture. Measure irregular sections separately and add or subtract them deliberately.
Editorial note: FixLume calculations are educational planning aids. We show the formula and assumptions so you can check the arithmetic yourself. Product-specific requirements should be verified against the exact manufacturer documentation and applicable local requirements.