# How much siding do I need?

Computes the siding a house needs: the wall and gable area less doors and windows, in squares, and the vinyl panels and cartons or fiber cement planks to buy, with waste.

- Page: https://www.acalculator.org/construction/siding-calculator
- JSON spec: https://www.acalculator.org/construction/siding-calculator.json
- Version: 62b6355adca6

## Default answer

Example with the default inputs (Total wall length 140 ft, Wall height 9 ft, Gables 2, Gable width 30 ft, Gable height 8 ft, Doors and windows 150 ft², Siding Vinyl, double 4 in (8 in exposure, 12 ft 6 in), Extra for waste 10%): 1,350 ft² of wall takes 179 pieces of siding (14.85 squares with waste).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| p | Total wall length | The length of all the walls to side, added up (the house perimeter). |
| h | Wall height | The height of the walls from the bottom of the siding to the eaves. |
| gab | Gables | How many triangular gable ends sit above the walls. |
| gw | Gable width | The width of one gable at its base. |
| gh | Gable height | The height of one gable from its base to the peak. |
| open | Doors and windows | The total area of the doors and windows in these walls, which takes no siding. |
| type | Siding | The siding product, which sets how much wall one piece covers. |
| exp | Exposure | The height of one piece that shows on the wall once it is lapped. |
| len | Piece length | The length of one piece of siding. |
| waste | Extra for waste | Siding to add, in percent, for cuts at corners, openings and gables. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| pieces | Pieces to buy | The area with waste ÷ the area one piece covers, rounded up. |
| cartons | Cartons | Pieces ÷ 24 per carton for the vinyl panels, rounded up. |
| area | Area to side | Walls + gables − doors and windows. |
| squares | Squares | The area in squares of 100 ft². |
| squaresWithWaste | Squares with waste | The area with the extra for waste, in squares of 100 ft². |
| cover | Covered by one piece | Exposure × piece length. |

## Method

Area = wall length × wall height + gables × width × height ÷ 2 − doors and windows; squares = area ÷ 100 ft²; pieces = ⌈area × (1 + waste ÷ 100) ÷ (exposure × piece length)⌉; vinyl cartons = ⌈pieces ÷ 24⌉.

## Assumptions

- Walls are rectangles of one height; each gable is a triangle.
- Vinyl double 4 in panels show 8 in and are 12 ft 6 in long, 24 to a carton (2 squares); fiber cement 8.25 in planks show 7 in and are 12 ft long. Other products: type the exposure and length.
- Waste is 10% by default. Trim, corners, starter strip, J-channel and soffit are not counted.

## Worked examples

1. p = 42.672, h = 2.7432, gab = 2, gw = 9.144, gh = 2.4384, open = 13.935456, type = vinyl, waste = 10% gives pieces = 179, cartons = 8, squares = 13.5, squaresWithWaste = 14.85. Source: CertainTeed Monogram vinyl siding, double 4 in (https://www.certainteed.com/products/siding-products/monogram, retrieved 2026-10-01), sold 24 panels of 12 ft 6 in to a carton (https://builderswarehouse.com/certainteed-monogram-double-4-siding-126-24-carton.html): 24 × 8 in × 12.5 ft = 200 ft², 2 squares.
2. p = 42.672, h = 2.7432, gab = 2, gw = 9.144, gh = 2.4384, open = 13.935456, type = plank, waste = 10% gives pieces = 213. Source: James Hardie HardiePlank lap siding (https://www.jameshardie.com/product-catalog/exterior-siding-products/hardie-plank-lap-siding/, retrieved 2026-10-01), 8.25 in × 144 in planks (https://www.lowes.com/pd/James-Hardie-8-25-in-x-144-in-HZ5-HardiePlank-Cedarmill-Lap-Siding/999968871) with a 7 in exposure.
3. p = 30.48, h = 2.4384, gab = 0, open = 0, type = plank, waste = 0% gives pieces = 115, squares = 8. Source: James Hardie HardiePlank lap siding, 8.25 in plank with a 7 in exposure, listed at 14.3 pieces per square (https://www.lowes.com/pd/James-Hardie-8-25-in-x-144-in-HZ5-HardiePlank-Cedarmill-Lap-Siding/999968871).

## FAQ

### How do I calculate how much siding I need?

Add up the wall area (total wall length × height), add each gable (width × height ÷ 2), and subtract the doors and windows. Add about 10% for waste, then divide by the area one piece covers. A 40 × 30 ft house with 9 ft walls, two 30 × 8 ft gables and 150 ft² of openings has 1,350 ft² to side.

### What is a square of siding?

100 square feet of wall. 1,350 ft² is 13.5 squares, or 14.85 squares with 10% waste.

### How many square feet does a box of vinyl siding cover?

A carton of double 4 in vinyl panels holds 24 panels of 12 ft 6 in with an 8 in exposure: 24 × 8 ÷ 12 × 12.5 = 200 ft², or 2 squares. Check the label: thick or specialty profiles may hold less.

### How many fiber cement planks are in a square?

An 8.25 in plank laps to a 7 in exposure, so a 12 ft plank covers 7 ÷ 12 × 12 = 7 ft². A square takes 100 ÷ 7 = 14.3 planks.

### What is exposure?

The height of a lap siding piece that shows once the next course overlaps it. It is less than the board width: an 8.25 in plank shows 7 in. Pick Other to type your own exposure and length.

### Does the calculator include trim?

No. Starter strip, J-channel, corner posts, soffit and fascia are bought by the length of edges and corners, not by area.

## Sources

- James Hardie, HardiePlank lap siding product page (8.25 in planks, 12 ft, 7 in exposure), retrieved 2026-10-01. https://www.jameshardie.com/product-catalog/exterior-siding-products/hardie-plank-lap-siding/
- HardiePlank 8.25 in × 144 in lap siding listing (7 in exposure, 14.3 pieces per square), Lowe’s, retrieved 2026-10-01. https://www.lowes.com/pd/James-Hardie-8-25-in-x-144-in-HZ5-HardiePlank-Cedarmill-Lap-Siding/999968871
- CertainTeed, Monogram vinyl siding product page (double 4 in clapboard profile), retrieved 2026-10-01. https://www.certainteed.com/products/siding-products/monogram
- CertainTeed Monogram double 4 in siding, 12 ft 6 in, 24 per carton, listing at Builders Warehouse, retrieved 2026-10-01. https://builderswarehouse.com/certainteed-monogram-double-4-siding-126-24-carton.html