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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.

Reviewed by the thecalcu.com team · Last updated July 9, 2026

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.

Why Use a Wall Square Footage Calculator?

Estimating paint or wallpaper needs from gross wall area alone leads to over-buying, since doors and windows can account for 10–20% of a wall's total area in rooms with multiple openings. This calculator gives you the precise net figure so your material estimate matches what you'll actually be covering.

A common use case is a homeowner planning to repaint a living room wall with a fireplace opening and two windows, entering the wall dimensions and the openings' sizes immediately shows the true paintable area, which then feeds directly into a paint-gallon calculation. Contractors quoting drywall or siding jobs can also use this calculator to quickly convert raw wall dimensions into the net figure needed for accurate material and labor estimates. If your project also involves gallon-per-square-foot coverage math for paint or coatings, the Gallons per Square Foot Calculator picks up where this one leaves off.

Who Should Use This Calculator?

  • Homeowners planning a paint or wallpaper project who want to avoid over-buying material.
  • Painting contractors quoting jobs who need accurate net wall area for material and labor estimates.
  • Drywall installers calculating gross area for sheathing, since framed openings still need drywall cut around them.
  • Siding contractors who need a net wall area figure as an input before applying wastage allowances.
  • Interior designers estimating wallpaper quantities for accent walls with windows or built-in features.

Anyone finishing a project with a topcoat may also want the Gallons per Square Foot Calculator to convert this area figure into paint or coating quantities.

What Insights Does the Wall Square Footage Calculator Give You?

The calculator returns two figures. Net Wall Area is the true coverable surface area after doors and windows are subtracted, this is the number to use for paint, wallpaper, or any finish material estimate. Gross Wall Area is the full rectangular wall area before any deductions, which is the figure needed for structural estimates like drywall sheathing or framing, where the wall cavity still needs to be built out to the openings.

Having both numbers lets you use the right figure for the right purpose, gross for structural materials, net for finish materials, without recalculating by hand each time. For siding specifically, feed your net area into the Vinyl Siding Calculator to get an order-ready square count with wastage included.

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.
Show formula & methodology ↓Show less ↑

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

How do I calculate wall square footage?
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.
What is the formula for net wall square footage?
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.
Why does gross wall area matter if I only need the net figure?
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.
What is the standard square footage of a door?
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.
How many square feet is a standard window?
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.
How do I use the Wall Square Footage Calculator?
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.
What is the difference between gross and net 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.
How much paint do I need based on my net wall area?
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.
Can I calculate square footage for multiple walls in a room?
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.
Does this calculator account for wall texture or trim?
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.
What's the difference between this and a siding calculator?
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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