Siding Square Footage Calculator

Add up the perimeter of all exterior walls, multiply by the wall height, and you have gross siding area. For a 30×40 ft single-story home with 9 ft walls, that's a perimeter of 140 ft × 9 ft = 1,260 sq ft.

Subtract the area of every door, window, and opening. Then add gable end areas if your home has gables. Finally, multiply by 1.10 to account for trim, overlap, and offcuts.

Gable ends are easy to miss. Each gable is a triangle: (base × height) / 2. For a 30 ft wide house with a 6/12 pitch roof, each gable is about 113 sq ft.

Two gables (front and back) add ~225 sq ft to your siding total — that's a meaningful chunk you don't want to leave out.

House siding is calculated by exterior wall surface area, which is different from house square footage (which measures interior livable space). To estimate siding correctly, you need the actual wall surface area accounting for gables, eaves, and overhangs.

Base calculation: house perimeter × wall height + gable triangles. For a 40 × 30 ft single-story house with 8 ft walls: perimeter (140 ft) × 8 ft = 1,120 sq ft of wall. Add gable triangles for the ends: 30 ft wide × 6 ft peak ÷ 2 = 90 sq ft per gable × 2 gables = 180 sq ft. Total: 1,300 sq ft.

Two-story house doubles the wall area. A 40 × 30 ft two-story: 1,120 × 2 + 180 = 2,420 sq ft of siding area.

Subtract major openings (windows >10 sq ft, doors): a typical house has 200-400 sq ft of windows and doors. Net siding area: 2,000-2,200 sq ft for the example two-story house.

Siding material choice dramatically affects total project cost. Per-square-foot installed costs (2024):

Vinyl siding: $3-7 per sq ft installed. Cheapest and most popular. 30-40 year lifespan.

Engineered wood (LP SmartSide, James Hardie ColorPlus): $4-9 per sq ft installed. Looks like wood, lasts 30+ years.

Fiber cement (James Hardie HardiePlank): $5-12 per sq ft installed. 50+ year warranty. Heavy and labor-intensive.

Aluminum siding: $4-8 per sq ft installed. Dents easily; less common today.

Wood (cedar lap, board-and-batten): $7-15 per sq ft installed. Requires staining every 5-7 years.

Stucco: $7-12 per sq ft installed. Most common in southwestern US and California.

Brick or stone veneer: $15-30 per sq ft installed. Premium material, premium labor.

Composite/synthetic stone: $10-20 per sq ft installed.

Siding alone isn't a full exterior project. A complete re-siding includes:

Tear-off of existing siding: $1-3 per sq ft.

House wrap / weather barrier: $0.20-0.50 per sq ft.

Trim around windows, doors, corners: $5-15 per linear foot.

Soffit and fascia (under the eaves): $8-20 per linear foot of eave.

Gutters (often replaced during siding work): $5-15 per linear foot.

Sealing and caulking: included in install labor.

For a 2,000 sq ft siding project, expect total cost of $10,000-30,000 fully installed depending on material. Vinyl is the cheap end ($8,000-14,000), fiber cement is the popular middle ($15,000-25,000), and natural wood or stone is the high end ($20,000-50,000+).