Home › Siding calculator
Siding Calculator: Squares, Boxes and Planks
Estimate how much siding a house needs: wall and gable area, minus doors and windows, plus waste. Get squares of vinyl, fiber cement planks, starter strip, J-channel and a material cost.
How to measure a house for siding
- Walls: measure around the house to get the perimeter, and multiply by the wall height from the bottom of the siding to the eaves.
- Gables: each triangular gable end is ½ × width × height. On a 6/12 roof over a 30 ft wide house, the gable is 7.5 ft tall, so 112.5 sq ft.
- Openings: subtract about 20 sq ft per door and 15 sq ft per average window. For big picture windows or garage doors, measure them.
- Waste: add 10% for a simple house and 15% for one with many corners, dormers or angled walls.
Siding is sold by the square, which is 100 sq ft of wall. Vinyl usually comes two squares to a box.
Worked example
A 40 × 30 ft ranch has a 140 ft perimeter and 10 ft walls, so 1,400 sq ft. Two gables add 225 sq ft. Two doors and ten windows take away 190 sq ft, leaving 1,435 sq ft. With 10% waste you need 15.8 squares: 8 boxes of vinyl, or about 226 fiber cement planks at 7 in exposure. At $150 per square for mid-grade vinyl, the material is about $2,370.
Siding costs by material
| Material | Material per square | Installed per square |
|---|---|---|
| Vinyl | $100 to $250 | $400 to $800 |
| Fiber cement (e.g. lap planks) | $150 to $350 | $700 to $1,400 |
| Engineered wood | $200 to $400 | $600 to $1,200 |
| Cedar | $400 to $800 | $900 to $1,600 |
Typical US ranges. Removing old siding, new house wrap and trim boards are extra.
Trim and accessories
- Starter strip runs along the bottom of every wall: one perimeter's worth.
- J-channel frames doors and windows (about 17 ft per door and 14 ft per window) and runs along the gable rakes and soffits.
- Outside corner posts are the height of the wall at each outside corner; inside corners can use J-channel or inside corner posts.
- Fiber cement planks are 12 ft long; an 8¼ in plank laid with 7 in showing covers 7 sq ft.
Painting instead? The paint calculator works for exterior walls too.
Frequently asked questions
How many squares of siding do I need for a 1,500 sq ft house?
A one-story 1,500 sq ft house usually has 1,400 to 1,800 sq ft of exterior wall including gables. After openings and 10% waste that is typically 15 to 19 squares.
What is a square of siding?
A square is 100 sq ft of wall coverage. Vinyl siding is usually packed two squares per box.
Do you subtract windows when measuring for siding?
Yes, subtract about 15 sq ft per window and 20 sq ft per door, but keep the 10% waste allowance because of the extra cuts around each opening.