How Do I Calculate How Much Siding I Need?
Multiply wall perimeter by wall height for gross area, add the gable triangles, subtract the doors and windows, add 10% waste, then divide by 100 to get squares. A house with a 140-foot wall perimeter and 9-foot walls is 1,260 square feet gross. Subtract two doors (21 sq ft each) and ten windows (15sq ft each) — 192 square feet of openings — for 1,068 net. Add 10% waste and it's about 11.7 squares.
Siding is estimated in squares— one square equals 100 square feet of wall. It's the unit siding is sold and priced in, so converting your wall area to squares makes ordering and comparing quotes simple. Vinyl often ships in boxes covering two squares; fiber cement and wood are sold by the piece but quoted by the square.
What Is a Square of Siding?
A square is 100 square feet of coverage. Contractors quote siding by the square for both material and labor. An 1,100-square-foot net wall is 11 squares. Always order a little over — running short mid-job means a second trip and a possible color-lot mismatch on vinyl.
How Much Waste Should I Add?
10% for a simple rectangular house with straight lap siding; 15% for many corners, dormers, and windows, or for shake and board-and-batten patterns. Waste covers the cut-offs around every opening and corner, the trim cuts at the end of each course, and the occasional damaged panel. Houses with lots of windows generate more offcuts because every opening interrupts the courses.
Do I Subtract Windows and Doors?
Yes — you don't side over openings. Subtract a standard door at about 21 square feet (3×7 ft) and a standard window at about 15 square feet (3×5 ft). For oversized units — picture windows, sliding-glass doors, garage doors — measure the real opening and deduct that. The calculator subtracts by opening count using standard sizes; adjust the counts to match your house.
How Do I Measure Gables?
A gable is a triangle — its area is ½ × base × height. A 24-foot-wide gable that rises 6 feet to the peak is ½ × 24 × 6 = 72 square feet. Add each gable into the "gable / extra area" field. A standard gable roof has two gable ends; a hip roof has none. Dormers and bump-outs go in the same field.
Vinyl vs. Fiber Cement vs. Wood vs. Metal
- Vinyl: Cheapest and lowest-maintenance — snaps together, never needs paint. Can crack in cold and fade over decades.
- Fiber cement (Hardie-style): Fire-, rot-, and insect-resistant; holds paint 15+ years. The most popular upgrade. Heavy and needs special blades to cut.
- Wood / engineered wood: Best natural look; needs regular paint or stain. Engineered wood (LP SmartSide) is lighter and more stable than solid cedar.
- Steel / aluminum: Durable and modern; steel resists fading but can dent. Common on contemporary and commercial exteriors.
Common Houses — Siding Estimates
Squares after typical openings and 10% waste; measure your actual walls for a firm number:
- Single-story ranch, 140 ft perimeter × 9 ft — ~11–12 squares
- Single-story, 160 ft perimeter × 9 ft — ~13–14 squares
- Two-story, 150 ft perimeter × 18 ft — ~26–29 squares
- Two-story with 2 gables, 160 ft × 18 ft — ~30–33 squares
Cost varies by region. The Estimated Material Cost card pulls from our indicative national-average pricing dataset (refreshed quarterly). Northeast and California metros run 15–40% above the national midpoint while Midwest and Southeast metros run 5–15% below — verify locally for binding quotes.
Related Calculators
- Insulation Calculator — Insulate the wall cavity before the siding goes on
- Gutter Calculator — Gutters and downspouts for the roof above
- Window Replacement Cost — Budget the windows in the same exterior project
- Roofing Calculator — Shingle bundles for the roof above the walls
- Paint Calculator — Gallons for painting wood or fiber cement siding
Written by Daniel McCarney — AceCalc