Square Footage of a Wall: How to Calculate

By RugCalc Editorial Team · Last updated: 2026-10-13 · 6 min read

Quick answer: multiply the wall's length by its height, then subtract the area of doors and windows. A 12-ft wall that's 8 ft tall is 96 sq ft; a whole bedroom usually lands around 300–350 sq ft of paintable wall.

Length × height

For a flat wall, the area is simply length × height. A 10-ft wall with 8-ft ceilings is 80 sq ft. Measure wall-to-wall (not baseboard-to-crown) and in whole feet plus inches — convert the inches to a decimal (6 in = 0.5 ft) for an accurate number.

Subtract openings

Doors and windows take up wall area you won't paint or cover. Subtract their square footage from the gross total. A standard door is about 21 sq ft (3 ft × 7 ft), and a typical double-hung window about 12–15 sq ft. Skipping this step makes you over-buy by 10–15%.

Wall area chart

Wall length	8-ft ceiling	9-ft ceiling
8 ft	64 sq ft	72 sq ft
10 ft	80 sq ft	90 sq ft
12 ft	96 sq ft	108 sq ft
14 ft	112 sq ft	126 sq ft

For a whole room, add all four walls, then subtract openings.

Worked example

A 12×12 bedroom, 8-ft ceilings:

• Gross walls: 4 walls × (12 × 8) = 384 sq ft
• Subtract 1 door (~21 sq ft) + 2 windows (~28 sq ft) = 49 sq ft
• Paintable wall area ≈ 335 sq ft

At 350 sq ft per gallon, that's about 1 gallon per coat — the paint calculator turns this into exact gallons.

Common mistakes

• Forgetting to subtract openings. Over-buys paint and wallpaper.
• Measuring baseboard to baseboard. That skips the top part of the wall.
• Rounding inches to the nearest foot. 6+ inches of rounding adds real area across a room.
• Counting trim as wall. Baseboards and casing aren't part of the flat wall.

FAQ