How this calculator works
Add the horizontal lengths of all walls being measured and multiply by their common height. For a rectangular room the total length is twice length plus width; a square uses four times its side. Door and window areas are deducted at their entered sizes. Open plans or one wall can use the known-total-length option.
Formula
Gross wall area = total wall length x common height; net wall area = gross area - doors x door width x door height - windows x window width x window height; height = (net area + opening area)/total wall length.
Worked example
A 3 m by 6 m rectangular room has an 18 m perimeter. At 2 m height its gross wall area is 36 m2. With no openings, that is also the net area.
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Frequently asked questions
Does this include ceiling area?
No. Add ceiling area separately for paint or drywall. The wall result uses vertical surfaces only.
Can walls have different heights?
Calculate groups with the same height separately and add their areas. A single common height does not model vaulted or sloping tops.
Can I show square feet?
Yes. Change the area output unit to ft2. Length inputs also support feet and inches, while the underlying area calculation stays consistent.