Exterior Square Footage Calculator
Measure exterior wall area for siding, paint, stucco, brick, or stone veneer. The gross wall area is the perimeter × wall height; subtract major openings and add gables.
Exterior Wall Calculator
Walls plus gables plus dormers
For a single-story rectangular house, exterior wall area = perimeter × wall height. A 40 × 30 ft house with 9 ft walls has a perimeter of 140 ft × 9 ft = 1,260 sq ft of wall.
Add gable triangles for a pitched roof. A 30-ft-wide gable end with a 7/12 pitch has a peak height of (30 ÷ 2) × (7 ÷ 12) = 8.75 ft. Triangle area = (30 × 8.75) ÷ 2 = 131 sq ft per gable. Two gables = 262 sq ft to add.
Dormers, bays, and bump-outs each get measured as their own additional wall section. Eave overhangs do not get sided but are included if you're painting.
What to subtract
For siding and stucco, subtract garage doors and any opening larger than 25 sq ft. For paint, subtract all door and window openings (you only paint the trim around them, calculated separately as linear feet).
A standard double garage door is 16 × 7 = 112 sq ft. A standard window is 3 × 5 = 15 sq ft. A typical single-story 2,000 sq ft house with a garage has 100-150 sq ft of openings to subtract.
Pro tips
Measure each wall as a rectangle
Don't multiply perimeter by height for a multi-story house with split-levels. Walk the foundation, measure each wall length, and multiply each by its actual height.
Don't forget chimneys
Chimney chases that get sided or painted add 4 sides × height. A 4-ft × 4-ft chimney chase 8 ft tall adds 128 sq ft.
Order siding by the square
Siding is sold by the "square" (100 sq ft). For 1,260 sq ft of wall, you need 12.6 squares + waste = 14 squares of siding minimum.
Stucco and stone need underlayment
Stucco coverage estimates assume the area is wired and prepped. Stone veneer adds a corner-piece line item (counted in linear feet of outside corners, not square feet).