Square Foot Calculator for Wall
Add multiple walls, deduct doors and windows, and get paint or wallpaper coverage estimates instantly.
Wall Dimensions
Deductions
Paint Options
How to Measure Wall Area
Measuring walls for paint, wallpaper, or siding requires calculating the total surface area and then subtracting any openings.
Step-by-Step
- Measure each wall: Measure the width and height of every wall you plan to paint.
- Calculate each wall area: Width × Height for each wall.
- Count openings: Count the number of standard doors and windows.
- Subtract deductions: A standard door is ~21 sq ft, a standard window is ~12 sq ft.
- Determine paint needed: Divide net area by coverage per gallon (usually 350 sq ft) and multiply by the number of coats.
Paint Coverage Guide
- Flat/Matte paint: ~350–400 sq ft per gallon
- Eggshell/Satin: ~350 sq ft per gallon
- Semi-gloss/Gloss: ~300–350 sq ft per gallon
- Primer: ~200–300 sq ft per gallon
Paint Coverage and Quantity Estimator
Once you have the net wall area (after subtracting doors and windows), use this guide to estimate how many gallons of paint you need. Most interior paints cover 350–400 sq ft per gallon per coat.
| Room Type | Typical Wall Area | Paint Needed (2 coats) |
|---|---|---|
| Small Bedroom (10×10, 8 ft ceiling) | ~280 sq ft | ~1.6 gallons |
| Average Bedroom (12×12, 8 ft ceiling) | ~320 sq ft | ~1.8 gallons |
| Living Room (16×20, 9 ft ceiling) | ~540 sq ft | ~3.1 gallons |
| Kitchen (12×14, 9 ft ceiling) | ~390 sq ft | ~2.3 gallons |
Pro tip: Always buy one extra quart for touch-ups and keep it labeled with the paint color and code.
Wallpaper Square Footage: Different Rules Apply
Wallpaper uses different calculations from paint. Rolls are sold in single or double rolls, and pattern repeat dramatically affects how much you need.
Standard Wallpaper Roll Coverage
- Single roll: Approximately 25–30 sq ft (US standard)
- Double roll: Approximately 55–60 sq ft (most common)
- European single roll: ~29 sq ft
Pattern Repeat Waste
If your wallpaper has a repeating pattern, each strip must be aligned, creating extra waste. Add the following to your total:
- No match (random): Add 10 %
- Straight across match: Add 15 %
- Drop match: Add 25–35 % depending on repeat size
Exterior Wall Siding and Cladding Estimates
The wall square footage calculator also works for exterior siding, cladding, brick, and stucco projects. Measure each exterior wall's width and height, subtract garage doors, windows, and any non-clad sections, then use the result to estimate your material quantity.
Exterior Siding Coverage per Square
Siding is sold in "squares" — 1 square = 100 sq ft. Divide your net exterior wall area by 100 to get the number of squares needed. Always add 10 % for waste and overlaps.
| Siding Type | Coverage per Square | Avg. Cost per Square |
|---|---|---|
| Vinyl Siding | 100 sq ft | $70 – $150 |
| Fiber Cement (Hardie) | 100 sq ft | $150 – $300 |
| Wood Lap Siding | 100 sq ft | $200 – $400 |
| Brick Veneer | 100 sq ft | $400 – $700 |
| Stucco (3-coat) | 100 sq ft | $300 – $500 |
| Stone Veneer | 100 sq ft | $500 – $900 |
All Square Foot Calculators
Choose a specialized calculator for your specific project type.
Frequently Asked Questions
A 12×12 room with 8 ft ceilings has 4 walls totaling 384 sq ft. After deducting a door (~21 sq ft) and a window (~12 sq ft), you get ~351 sq ft. That's about 1 gallon for one coat, or 2 gallons for two coats.
Generally no — baseboards and trim take negligible area. However, if you're painting trim a different color, measure them separately.
Most projects need 2 coats. If you're covering a dark color with a lighter one, you may need a primer coat plus 2 top coats (3 total).
Yes! Calculate your net wall area with this tool. Then divide by the coverage of your wallpaper roll (usually 25-28 sq ft per single roll) to determine how many rolls to buy.