Wall Surface Area

Room Wall Square Footage Calculator

Enter your measurements and get the area instantly — in square feet, yards, meters and more. Add a price to estimate material cost for flooring, paint or tile.

Open Calculator Read the Guide
Room Walls (Four Walls)area
perimeter × height − openings
Room Walls (Four Walls)
Area = 2 × (L + W) × H − openings
FormulaArea = 2 × (L + W) × H − openings
Ceiling Ht L × W footprint perimeter × height perimeter × height − openings

How to Calculate the Total Square Footage of a Room's Walls

When you are painting or wallpapering, the number you need is not the floor area — it is the combined surface area of the four vertical walls. This calculator works out that total from the room's length, width and ceiling height, then subtracts standard doors and windows so you are not buying material to cover openings. It is the go-to tool for estimating paint, primer, wallpaper and wall coverings.

The four-walls formula

The walls around a rectangular room form a band whose length is the room's perimeter and whose height is the ceiling height:

Wall area = 2 × (Length + Width) × Ceiling height − openings

The perimeter is 2 × (length + width); multiplying by the ceiling height gives the gross wall area. The calculator then subtracts a standard door (3 × 7 ft = 21 sq ft) and window (3 × 4 ft = 12 sq ft) for each one you enter.

Measuring the room

  • Length and width: Measure the two floor dimensions wall to wall.
  • Ceiling height: Measure floor to ceiling; most rooms are 8, 9 or 10 feet.
  • Doors and windows: Count how many of each the room has. The calculator assumes standard sizes; if yours are unusually large, treat the result as an estimate or subtract the difference manually.

Worked example

For a 12 × 10 foot room with 8-foot ceilings, one door and two windows:

Perimeter = 2 × (12 + 10) = 44 ft. Gross wall area = 44 × 8 = 352 sq ft. Subtract one door (21) and two windows (24): 352 − 45 = 307 square feet of paintable wall.

To turn that into paint: divide 307 by the coverage on the can (say 375 sq ft per gallon) and multiply by two coats — roughly 1.6 gallons, so two gallons with a little to spare.

From wall area to material

Paint cans list a coverage rate, commonly 350–400 square feet per gallon for one coat. Divide your wall area by that rate, then multiply by the number of coats (usually two) to get gallons. For wallpaper, divide the wall area by the usable coverage per roll, and add 10–15% for pattern matching and trimming. Primer is figured the same way as a single coat.

Related shape calculators

For the floor or ceiling of the same room, use the rectangle calculator. For a suspended ceiling and its tile count, see the drop ceiling calculator, and for an exterior gable end the gabled wall calculator.

Frequently Asked Questions

How do I calculate the square footage of all four walls?
Add the length and width, double it for the perimeter, then multiply by the ceiling height. Subtract the area of doors and windows. The calculator does this once you enter the dimensions and opening counts.
What size are the standard doors and windows used here?
The calculator assumes a 3 × 7 ft door (21 sq ft) and a 3 × 4 ft window (12 sq ft). Adjust the counts to your room; for unusual sizes, treat the total as an estimate.
How much paint will I need?
Divide the total wall area by the coverage rate on the paint can (commonly 350–400 sq ft per gallon), then multiply by the number of coats you plan, usually two.
Why calculate wall area instead of floor area for painting?
Paint covers the vertical walls, not the floor. Wall area depends on the room's perimeter and ceiling height, which is a different figure from the floor's length × width.
How many square feet of wall is a 12×10 room with 8 ft ceilings?
About 352 sq ft gross; subtracting one standard door and two windows leaves roughly 307 sq ft to paint.
Should I include the ceiling in this total?
No, this figure is the walls only. For the ceiling, use the floor area (length × width) from the rectangle calculator and add it separately if you are painting it too.
How do I estimate wallpaper instead of paint?
Divide the wall area by the usable coverage per roll, then add 10–15% for pattern matching and trimming around openings.
Can I subtract more than one door or window?
Yes. Enter the actual counts of doors and windows and the calculator subtracts a standard size for each.