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Wall Area Calculator
Enter the width and height of each wall, then subtract doors, windows or other areas you will not cover. Calculate one wall or several in square feet or square meters.
Calculate net wall area
How to calculate wall area
Measure the full width A and height B of one wall. Use the same units for both dimensions.
Wall area before openings = width × height
A wall 12 ft wide and 8 ft high measures 96 sq ft before any openings are subtracted. In meters, width × height gives square meters.
Use Add another wall for a different wall. Naming each one, such as kitchen wall or living room north wall, helps keep its doors and windows with the correct measurements.
You do not need a whole room’s length, width and height to calculate a single wall.
Subtract doors, windows and other openings
Measure each opening’s width and height. Under the wall it belongs to, choose Subtract section → Window, Door or Other section. An opening is deducted from that wall only.
Net wall area = wall area + added sections − subtracted sections
Use Quantity when several openings have exactly the same dimensions. For different sizes, add separate sections. Do not count the same opening twice or let subtracted areas overlap.
Subtract only the surfaces you will leave uncovered. Check the product or job requirements when deciding whether an opening should be deducted. For an extra part of the same wall, such as a triangular top, use Add section.
A wall with a sloped top
Choose Wall with a sloped top for one straight sloping top and two vertical ends. Measure width A, left height B and right height D.
Wall area = width × (left height + right height) ÷ 2
A 10 ft wide wall with heights of 8 ft and 12 ft measures 100 sq ft before openings. Enter the two actual end heights rather than estimating the average yourself.
For a pointed top, use a rectangular main wall and add a triangular section. A wall with several changes in height can be split into non-overlapping sections.
Feet and inches or metric measurements
For a wall 12 ft 6 in wide, enter 12 in the ft box and 6 in the in box. The calculator converts inches before multiplying. For inches only, leave ft blank; fractional inches such as 6 1/2 are supported.
Choose Feet (ft) for a single decimal input such as 12.5. In ft + in mode, leave in blank or 0 when entering decimal feet. Meters, centimeters and millimeters are also available; metric area is shown in m².
Example: a wall with one window and one door
12 ft wide × 8 ft high
- Wall before openings: 12 × 8
- 96 sq ft
- Subtract window: 3 × 4
- 12 sq ft
- Subtract door: 3 × 7
- 21 sq ft
- Net wall area: 96 − 12 − 21
- 63 sq ft
Example measurements are separate from your own.
Use net wall area for a material estimate
After measuring, optionally open Estimate materials & cost. Choose only the completed walls using the same product, enter a waste allowance and use the coverage and price from its label. A new incomplete wall cannot be selected; if a selected wall becomes incomplete, the estimate pauses.
The four steps can be opened independently. Waste and whole-box rounding change the purchase quantity, while the measured net wall area stays unchanged.
For example, 63 sq ft with a chosen 10% allowance needs 69.3 sq ft. With 20 sq ft per box, buy 4 boxes covering 80 sq ft. An example price of $5 per sq ft gives $400 in material cost. These waste and price values are examples, not product standards.
This estimates coverage by area or box. It does not calculate paint gallons, coat counts, wallpaper rolls or installation labor. Tax and delivery are not automatically included.
Estimate materials for your walls →Wall area calculator questions
Can I calculate all the walls in a room?
Yes. Add each wall separately with its own width, height and openings. The total combines their net areas; it does not multiply a single wall into a whole-room estimate.
Do I always subtract doors and windows?
Subtract them only when your intended measurement excludes those surfaces. Keep every deduction with its wall, and check the product or job requirements before ordering.
Can several windows share one entry?
Yes, if their dimensions match. Enter one window’s width and height, then its quantity. Use separate entries for different sizes.
Why is the net area incomplete?
A main wall, added section or deduction still needs valid measurements. Complete it or remove an unused section. Deductions cannot exceed the wall and its added sections.
Can I reuse a saved calculation?
When you open this page, the previous-calculations prompt lets you explicitly choose a saved wall calculation. Floor measurements are not converted into wall width and height. Starting new keeps the original drafts and opens blank inputs.
Content updated October 16, 2026.