Wall Square Footage Calculator
Find the square footage of your walls for painting, drywall or wallpaper. Measure a whole room or add walls one by one, subtract windows and doors, and get the net wall area — plus gallons of paint, sheets of drywall, rolls of wallpaper and an optional cost, with by-wall and by-height tables and a downloadable PDF.
| Wall | Width | Height | Area |
|---|---|---|---|
| Enter your walls to see each area | |||
| Height | Net area | Paint | Drywall | Wallpaper |
|---|---|---|---|---|
| Enter your walls to compare heights | ||||
How to use the wall square footage calculator
Four quick steps turn your room or walls into the net wall area — plus the paint, drywall, and wallpaper to buy, with by-wall and by-height tables and a downloadable report.
Measure the walls
Enter a whole room’s length, width, and height, or add walls one by one for odd shapes.
Subtract openings
Add your windows, doors, and any other areas you won’t cover — they come off the total.
Set materials
Choose paint coats and coverage, drywall sheet size, waste, and an optional ceiling.
Read results & save a PDF
Get the net area, gallons, sheets, and rolls, with a cost option — then download a report.
How the wall area is calculated
Each wall is width times height; a room is the perimeter times the height; openings come off, then materials follow from the net area. Here is the exact math the calculator runs.
Worked example — 14 × 12 ft room, 8 ft walls, 2 windows (3×4), 1 door (3×6.67), 2 coats
Gross: 2 × (14 + 12) × 8 = 416 sq ft
Openings: 2 × 12 + 1 × 20 = 44 sq ft → Net: 416 − 44 = 372 sq ft
Paint: 372 × 2 / 350 ≈ 2.1 gal → buy 3 · Drywall: 372 × 1.10 / 32 ≈ 13 sheets
≈ 372 sq ft net, ~3 gallons of paint, ~13 sheets of drywall.
Wall area reference charts
Handy lookups for opening sizes, material coverage, and how ceiling height changes the area. These are typical US figures — check the product label for exact coverage.
| Opening | Size | Area |
|---|---|---|
| Interior door | 3 × 6.67 ft (36 × 80 in) | ~20 sq ft |
| Standard window | 3 × 4 ft | 12 sq ft |
| Large window | 3 × 5 ft | 15 sq ft |
| Patio / sliding door | 6 × 6.67 ft | ~40 sq ft |
Measure your actual openings where you can — these averages are for quick planning.
| Material | Covers | Note |
|---|---|---|
| Paint (per gallon) | 350–400 sq ft | Per coat, smooth walls |
| Drywall 4 × 8 ft | 32 sq ft | Easiest to handle |
| Drywall 4 × 12 ft | 48 sq ft | Fewer seams |
| Wallpaper double roll | ~56 sq ft | ~50 usable after matching |
Textured or porous walls cover less per gallon. Round up to whole gallons, sheets, and rolls.
| Ceiling | Gross wall area | vs. 8 ft |
|---|---|---|
| 8 ft | 416 sq ft | — |
| 9 ft | 468 sq ft | +12% |
| 10 ft | 520 sq ft | +25% |
| 12 ft | 624 sq ft | +50% |
Height multiplies the whole perimeter, so it has a big effect. Measure the real floor-to-ceiling height.
Everything the calculator works out
A room or a wall list gives you the gross and net area, plus the paint, drywall, and wallpaper to buy — with per-wall detail and a height comparison.
Key figures behind the estimate
Built for any wall project
From a weekend repaint to a drywall job, the same calculator turns a room into a net area and a shopping list.
Repainting a room and wants to buy the right number of gallons without over- or under-ordering.
- Enter room & openings
- Set coats & coverage
- Read gallons to buy
Hanging drywall or wallpaper and needs the sheet and roll counts with waste built in.
- Pick sheet size & waste
- Add the ceiling if needed
- Read sheets & rolls
Needs a fast net-area figure and cost per square foot across one or several rooms.
- List individual walls
- Add a price per sq ft
- Attach the PDF to the quote
7 things to know about measuring walls
A few details keep a wall estimate accurate and your material buy on the money.
Wall square footage calculator FAQ
The measuring and material questions people ask most about wall area.
For a single wall, multiply its width by its height. A wall 12 feet wide and 8 feet tall is 12 times 8, or 96 square feet.
For a whole room, the quickest way is to add up the lengths of all the walls (the room’s perimeter) and multiply by the ceiling height. A rectangular room is 2 times (length plus width) times height — so a 14 by 12 foot room with 8-foot walls is 2 times 26 times 8, which is 416 square feet of wall.
That gives the gross wall area. Subtract the windows, doors and any other openings to get the net area you will actually paint, drywall or paper.
For most projects, yes — subtracting the openings gives a more accurate figure and avoids buying too much material. Measure each window and door (width times height) and take their total area off the gross wall area.
A standard interior door is about 3 by 6.67 feet, or roughly 20 square feet, and a typical window is around 12 to 15 square feet. On a room with several of each, that can add up to a meaningful amount.
The exception is small jobs where the leftover material is useful insurance: some painters skip deducting small windows so they have a little extra. For drywall and wallpaper, always subtract the large openings.
Divide the net wall area by the paint’s coverage, then multiply by the number of coats. Most interior paints cover about 350 to 400 square feet per gallon on smooth walls, and two coats is standard for a color change or new drywall.
For example, 400 square feet of wall at 350 square feet per gallon needs about 1.1 gallons per coat, or roughly 2.3 gallons for two coats — so you would buy 3 gallons, or a 2-gallon plus a 1-gallon.
Textured or porous walls drink more paint, so they cover less per gallon. Always round up to whole containers and keep some left over for touch-ups.
Divide the total area to cover by the area of one sheet, then add a waste allowance and round up. A 4 by 8 foot sheet is 32 square feet, a 4 by 10 is 40, and a 4 by 12 is 48 square feet.
For example, 450 square feet of wall with a 10 percent waste allowance is about 495 square feet, which is roughly 16 sheets of 4 by 8 foot drywall once you round up.
Larger sheets mean fewer seams to tape and finish, but they are heavier and harder to handle in tight spaces. Add the ceiling area if you are drywalling it too, and remember you will also need joint compound, tape and screws.
Divide the net wall area by the usable coverage of a roll and round up, adding extra for pattern matching. A standard US double roll covers about 56 square feet of wall, but usable coverage after trimming and matching the pattern is often closer to 50 square feet.
For example, 400 square feet of wall needs about 8 double rolls at 56 square feet each before waste, so with a 15 percent allowance for pattern repeat you would buy 9 or 10.
Patterns with a large repeat waste more, so add more for those. Buy all the rolls from the same batch or run number so the color and pattern match across the whole room.
The standard ceiling height in most older US homes is 8 feet, which is the default many calculators and estimates assume. Many newer homes have 9-foot ceilings on the main floor, and some have 10 feet or more.
Ceiling height matters a lot for wall area, because it multiplies the entire perimeter. Going from an 8-foot to a 9-foot ceiling adds about 12 percent to the wall area, and a 10-foot ceiling adds 25 percent over 8 feet.
Measure the actual floor-to-ceiling height rather than assuming, especially in older homes where ceilings can be irregular or in rooms with raised or vaulted ceilings.
Break the room into individual walls and measure each one separately, then add the areas together. This is the most reliable method for L-shaped rooms, rooms with bump-outs or alcoves, and any space that is not a simple box.
Measure each wall’s width and height, multiply to get its area, and sum them all. For an accent wall or a single exterior wall, you only need that one wall’s width and height.
For sloped or gable walls, treat the triangular part as half the base times the height and add it to the rectangular portion below. Measuring wall by wall also lets you handle different ceiling heights in the same room.
Only if you are finishing the ceiling too. Wall square footage normally means just the vertical walls, but if you are painting or drywalling the ceiling, add its area — the room’s length times its width — to the total.
For a 14 by 12 foot room, the ceiling adds 168 square feet, which is a significant amount of extra paint or drywall on top of the walls.
Keep the ceiling separate in your planning if it needs a different product — for example a flat ceiling paint versus a washable wall paint — even though the raw area adds into the same material total. This calculator lets you include or exclude the ceiling with one setting.
Estimate only — confirm with your supplier. This calculator finds wall area from the dimensions you enter (width × height per wall, or perimeter × height for a room), minus the windows, doors, and other openings you list, in US units. Paint quantities use the coverage you enter, and drywall and wallpaper add your waste allowance and round up to whole sheets and rolls — real coverage varies with wall texture, porosity, paint, and technique, so check the product label for actual figures. The optional cost is a rough estimate from the price per square foot you enter and excludes primer, supplies, and labor unless you include them. For planning purposes only.