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Wall Square Footage Calculator

Construction

Calculate net wall square footage after subtracting doors and windows. Get gross and paintable area for paint, wallpaper, or siding project estimates.

1500
130
1
1040
2
540

Net Wall Area

129
Gross Wall Area
180

This calculator computes your Net Wall Area, Gross Wall Area from the values you enter.

Inputs
Wall LengthWall HeightNumber of DoorsDoor Area (each)Number of WindowsWindow Area (each)
Outputs
Net Wall AreaGross Wall Area

What is a Wall Sq Ft?

A Wall Square Footage Calculator determines the net, coverable area of a wall after subtracting the space taken up by doors and windows. This net figure — not the raw length-times-height gross area — is what matters for estimating paint, wallpaper, tile, or siding material, since you're never covering the openings themselves. Getting this number right the first time avoids buying too much material or running short mid-project.

This tool is built for homeowners, painters, and contractors who need an accurate coverable area for a single wall. Enter the wall's dimensions along with the number and size of doors and windows, and the calculator instantly returns both the gross area (useful for framing or drywall sheathing estimates) and the net area (useful for finish materials). If you're using this figure to plan exterior cladding, the Vinyl Siding Calculator takes net area and converts it into an order-ready materials estimate.

How to use this Wall Sq Ft calculator

  1. Enter the Wall Length in feet.
  2. Enter the Wall Height in feet.
  3. Enter the Number of Doors on this wall, and set the Door Area per door in square feet (21 sq ft is standard).
  4. Enter the Number of Windows on this wall, and set the Window Area per window in square feet (15 sq ft is a common average).
  5. Review the Net Wall Area result for paint, wallpaper, or siding estimates, and check Gross Wall Area for structural material planning.

Formula & Methodology

The calculator computes gross area, then subtracts door and window openings:

Gross Area (sq ft) = Wall Length × Wall Height

Net Area (sq ft) = max(0, Gross Area − (Number of Doors × Door Area) − (Number of Windows × Window Area))

Worked example: A 20 ft × 9 ft wall with 1 door (21 sq ft) and 2 windows (15 sq ft each):

Gross Area = 20 × 9 = 180 sq ft

Net Area = 180 − (1 × 21) − (2 × 15) = 180 − 21 − 30 = 129 sq ft

Frequently Asked Questions

Multiply the wall's length by its height to get the gross area in square feet, then subtract the area of any doors and windows to get the net, paintable area. This net figure is what you use for paint, wallpaper, or siding coverage estimates, since you're not covering the openings.
Gross Area = Wall Length × Wall Height, and Net Area = Gross Area − (Number of Doors × Door Area) − (Number of Windows × Window Area). The result is the actual surface area you need to cover with paint, wallpaper, or siding material.
Gross area is useful for structural material estimates like framing or drywall sheathing, where the openings still need to be framed even though they're not covered with the final surface material. Net area is what matters for finish materials like paint or wallpaper, where you're only covering solid wall surface.
A standard interior or exterior door is about 21 square feet, based on a common 3-foot by 7-foot opening including the frame. Larger doors like double-entry doors or garage-adjacent doors can be significantly bigger, so measure directly if your doors aren't standard size.
A standard residential window averages around 15 square feet, though this varies widely from small bathroom windows (as little as 5 sq ft) to large picture windows (30 sq ft or more). Measure width times height for each window type if your home has non-standard sizing.
Enter the Wall Length and Wall Height in feet, then enter the Number of Doors and Number of Windows along with their individual area in square feet. The calculator returns both the Net Wall Area and the Gross Wall Area.
Gross wall area is the full rectangular area of the wall (length × height) with no deductions, while net wall area subtracts the space taken up by doors and windows. Paint and wallpaper coverage should always use net area to avoid buying excess material.
Most paint covers approximately 350–400 square feet per gallon for a single coat, so divide your net wall area by that coverage rate to estimate gallons needed. For two coats, double the gallon estimate, and always round up to the nearest full gallon or quart.
This calculator handles one wall at a time. Calculate each wall separately using its own length, height, doors, and windows, then add the net area results together for a full room total.
No — this calculator estimates flat surface area only. Textured walls may need slightly more paint due to surface area increases from texture, and trim, baseboards, and crown molding are typically calculated separately by linear foot.
This calculator gives you net wall area for a single wall, which is a useful input for the [Vinyl Siding Calculator](/vinyl-siding-calculator/) if you're planning exterior cladding — siding calculations then add a wastage allowance and convert to industry-standard "squares".
Also known as
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