Wall area drives the quantity of paint, wallpaper, drywall, panelling and tile. Measure each wall at floor level, multiply by the ceiling height and subtract openings that will not be covered. Standard openings are about 21 ft² for a door and 15 ft² for a window, but you can set your own sizes.
How to use the Wall Square Footage Calculator
- Measure
- Room length / wall length
- Room width
- Ceiling height
- Doors
- Door size (area)
- Windows
- Window size (area)
- Include ceiling
- Price (optional)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose a full room or a single wall, enter the dimensions, the number and size of doors and windows and whether to include the ceiling. The calculator returns the gross, opening and net areas and the cost at your price per unit area.
Tips for an accurate estimate
- Sketch the job and split irregular areas into rectangles, circles and triangles before you measure.
- Add a waste allowance – typically 5–10% for simple layouts and 15–20% for diagonal, curved or heavily cut work.
- Check the coverage or yield printed on the product, because sizes and densities vary between manufacturers.
- Buy all units of a finished material (tile, brick, siding) from the same batch so colours match, and keep a few spares for repairs.
- Confirm local prices – quarry, lumber and steel prices vary widely by region and season.
Common mistakes to avoid
- Ordering exactly the calculated amount with no allowance for breakage, offcuts and settlement.
- Forgetting to subtract doors, windows and other openings – or subtracting small ones that still need cutting around.
- Confusing US short tons (2,000 lb) with metric tonnes (1,000 kg) when comparing quotes.
Inputs explained
| Field | What to enter |
|---|---|
| Measure | Choose one: Whole room (4 walls), Single wall |
| Room length / wall length | Units: ft, m, in, yd, cm |
| Room width | Units: ft, m, in, yd, cm |
| Ceiling height | Units: ft, m, in, yd, cm |
| Doors | A number |
| Door size (area) | Units: ft², m², yd², acre |
| Windows | A number |
| Window size (area) | Units: ft², m², yd², acre |
| Include ceiling | Choose one: No, Yes |
| Price (optional) | Units: /ft², /m², /yd² |
What each result means
- Openings = [Doors]×[Door size (area)] + [Windows]×[Window size (area)]
- Net wall area = max([Gross wall area] – [Openings], 0)
- Cost = [Total area to cover]×[Price (optional)]
Example values
How the main result changes when Room length / wall length changes and everything else stays at the example values above:
| Room length / wall length (ft) | Total area to cover (ft²) |
|---|---|
| 7 | 253 |
| 10.5 | 309 |
| 14 | 365 |
| 17.5 | 421 |
| 21 | 477 |
| 28 | 589 |
Formula
Walls = 2 (L + W) × H (room) or L × H (single wall)Net = walls − doors × door area − windows × window areaTotal = net + ceiling (optional)Worked example
Inputs — Measure: Whole room (4 walls); Room length / wall length: 14 ft; Room width: 12 ft; Ceiling height: 8 ft; Doors: 1; Door size (area): 21 ft²; Windows: 2; Window size (area): 15 ft²; Include ceiling: No; Price (optional): $0 /ft².
Results — Gross wall area = 416 ft²; Openings = 51 ft²; Net wall area = 365 ft²; Total area to cover = 365 ft²; Cost = $0.00.
Frequently asked questions
How do I calculate the square footage of a wall?
Multiply the wall length by its height, then subtract doors and windows.
What size is a standard door and window?
About 3 × 7 ft (21 ft²) for doors and 3 × 5 ft (15 ft²) for windows.
Should I subtract small windows?
For paint, small openings are often ignored because cutting in uses extra paint; subtract them for wallpaper or panels.
What formula does the Wall Square Footage Calculator use?
Walls = 2 (L + W) × H (room) or L × H (single wall).