Wall Square Feet Calculator
Net Wall Area
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Wall Diagram
InteractiveHow to Calculate the Square Feet of a Wall
Wall square footage is the vertical surface area you need to cover with paint, wallpaper, tile, or cladding. Unlike floor area, which is horizontal, wall area is measured by multiplying the wall's length by its height. Openings such as doors and windows are subtracted to give you the net paintable or coverable area.
Basic Wall Area Formula
Measure the full length of the wall from corner to corner, and the full height from floor to ceiling. Multiply them to get the gross wall area. If you're painting four walls, calculate each wall separately or calculate one and multiply by the number of identical walls.
Wall Area Formula
FormulaExample: 15 ft wall × 9 ft ceiling − 21 sq ft door = 114 sq ft
Subtracting Doors and Windows
A standard interior door is approximately 3 × 7 ft = 21 sq ft. A standard window is roughly 3 × 4 ft = 12 sq ft. Use the "+ Add Opening" feature in the calculator to subtract any number of doors, windows, or architectural niches from the gross wall area automatically.
Which Direction to Measure?
Always measure the wall's interior surface — not the exterior. In most residential construction, interior walls are measured from corner to corner at baseboard level. The height is measured from the finished floor surface to the ceiling (not to the top plate).
What Wall Square Footage Is Used For
Paint Quantity Estimation
Interior paint covers roughly 350–400 sq ft per gallon. Divide your net wall area by 350 (conservative) to find the number of gallons needed for one coat. For two coats, double the result. Textured or porous surfaces absorb more — reduce coverage to 300 sq ft per gallon.
Wallpaper and Tile Coverage
Wallpaper rolls typically cover 25–30 sq ft. Divide your net wall area by the roll coverage to determine how many rolls to purchase. For wall tile, add 10–15% waste to your net area and divide by the tile's stated coverage per box.
Drywall and Cladding
Drywall sheets are standardized at 4 × 8 ft (32 sq ft) or 4 × 12 ft (48 sq ft). Add 10% waste to your net wall area and divide by sheet size to calculate the number of sheets needed for a new room or remodel.
Insulation Estimation
Batt insulation is rated by wall cavity size and sold in packages covering a stated square footage. Calculating net wall area (excluding openings) gives you the correct total insulation required for an energy-efficient installation.
Frequently Asked Questions
Multiply the wall's length by its height. For example, a wall that is 15 feet long and 9 feet tall equals 135 square feet. Subtract any doors or windows to get the net wall area.
Most interior paints cover 350–400 square feet per gallon. For rough or porous surfaces, plan for 300 sq ft. Always buy slightly extra to account for touch-ups and second coats without color batch differences.
Yes for precision budgeting. A standard door opening (21 sq ft) and window (12 sq ft) can add up to nearly a full gallon of paint savings on a large room. Use our deduction feature to subtract them automatically.
Calculate the perimeter (2 × Length + 2 × Width), then multiply by the ceiling height. For a 12×10 room with 9 ft ceilings: (2×12 + 2×10) × 9 = 44 × 9 = 396 sq ft of gross wall area before subtracting openings.
A standard interior door is 32–36 inches wide and 80 inches tall. That equals approximately 17.8–20 square feet. A common industry shorthand is 21 sq ft to account for the frame opening.
12 feet × 9 feet = 108 square feet. This is common for a living room accent wall. After subtracting one standard door (21 sq ft), the net area would be 87 square feet.
Calculate the net wall area (after subtracting windows and doors). Divide by the wallpaper roll's coverage (typically 25–30 sq ft per single roll, or 56 sq ft per double roll). Always add one extra roll for pattern matching and waste.
Yes — both use Length × Width. For floors, Width is the room's width. For walls, "Width" is the ceiling height. The formula is identical; only the dimensions being measured differ.