Wall Square Footage Calculator
Accurately calculate surface area for painting, tiling, or wallpaper projects.
How to Calculate Square Feet of a Wall
Whether you are planning a DIY painting project or hiring a contractor for wallpaper installation, knowing how to calculate the square footage of a wall is a fundamental skill. The process involves basic geometry but requires careful measurements to ensure you don't overbuy materials.
The Basic Wall Area Formula
The standard formula for calculating the area of a single rectangular wall is:
Length (ft) × Height (ft) = Total Square Feet
For example, if you have a wall that is 15 feet long and 8 feet high, the calculation is 15 x 8 = 120 square feet.
Accounting for Doors and Windows
Most walls are not solid blocks of drywall; they contain interruptions like doors and windows. To get the net paintable area, you must subtract these openings from your total. Standard sizes used in our calculator are:
- Standard Door: Approximately 21 square feet (3′ x 7′).
- Standard Window: Approximately 12 square feet (3′ x 4′).
Step-by-Step Calculation Example
Let's say you want to calculate the area for a room with four walls, each 10 feet long and 8 feet high, with one door and two windows.
- Calculate Gross Area: 10ft (L) x 8ft (H) = 80 sq ft per wall. 80 x 4 walls = 320 sq ft.
- Determine Deductions: 1 Door (21 sq ft) + 2 Windows (24 sq ft) = 45 sq ft total deduction.
- Calculate Net Area: 320 sq ft – 45 sq ft = 275 square feet.
Why Precision Matters
Underestimating square footage leads to mid-project runs to the hardware store, which can result in "flashing" or color mismatch if the paint batch numbers don't align. Overestimating leads to wasted money and unnecessary storage of leftover supplies. As a rule of thumb, one gallon of paint typically covers about 350 to 400 square feet.