What is a square of siding?

100 square feet of finished wall. Siding, roofing and some cladding are all sold and quoted by the square, and a box of vinyl siding usually covers two of them.

How much siding waste should I allow?

Ten per cent for a simple rectangular house, 15 for one with a few dormers or angles, and up to 20 where there are many corners, gables or windows. The waste is offcuts, not breakage.

How do I measure a gable end for siding?

Take the width at the eaves and the vertical height to the peak, then halve the product. The tool does the halving when you mark the section as a gable.

Does the calculator include trim and corner posts?

It estimates the linear feet, adding the perimeter of every opening to the height of the outside corners. Order the profiles by that figure, allowing for the lengths your supplier stocks.

What is exposure and where do I find it?

The visible height of each course after the lap, and it is on the product's installation sheet. Vinyl usually quotes it in the profile name — a double-4 panel exposes two four-inch courses per piece.

Siding Calculator

Work out the siding a house needs from wall sizes, gables and openings, in squares and in boxes.

The Siding Calculator runs entirely in your browser. Wall measurements and prices are calculated on your device.

Estimate the roof too

About Siding Calculator

Siding is estimated in squares — 100 square feet of finished wall — and then ordered in whatever the product happens to come in: boxes of vinyl, single lap boards, or sheets of panel. What ties the two together is the exposure, the visible height of each course once it laps the one below. An eight-inch board laid with a seven-inch exposure covers seven inches of wall, and that one detail is where most hand estimates go wrong. This calculator adds up walls and gables, takes off the windows and doors, applies a waste allowance, and converts the result into squares and into a count of whatever you are buying, with the trim run and the material cost alongside.

Features

Adds up any number of walls, with gables counted as half their rectangle
Subtracts windows and doors, or leaves them in if you prefer to cover the cutting
Waste allowance applied on top, with guidance on what to use
Converts to squares, boxes of vinyl, lap boards or sheet panels
Board counts derived from exposure rather than board width
Courses up the tallest wall, and the linear feet of board needed
Trim estimate for corners and openings, plus total material cost
Works in feet or metres

How to use the Siding Calculator

List each wall with its width, height and how many identical ones there are
Mark gable ends so they count as triangles
Add the windows and doors to subtract
Pick how the siding is sold and read the number of boxes, boards or panels

Example

Input

40×10 front and back, two 25×10 sides, two 25×8 gables, 8 windows and 2 doors, 10% waste

Output

1,500 sq ft gross − 138 sq ft openings = 1,362 → 1,498 sq ft with waste ≈ 15 squares

Eight boxes of two-square vinyl covers it, with a little in hand for the cuts.

Common errors & troubleshooting

The board count seems far too high. — Check the exposure rather than the board width. A 12-foot board with a 7-inch exposure covers 7 square feet, not 12 — the difference is the lap.
The estimate comes out short on site. — Raise the waste allowance. Ten per cent suits a plain rectangle; dormers, bay windows and lots of corners need 15 to 20 because every cut leaves an offcut too short to use.
Should small windows be deducted at all? — Many estimators leave openings under about 10 square feet in, on the grounds that the extra cutting around them uses the material anyway. The switch here lets you do it either way.
The gable area looks wrong. — Enter the full width of the gable and its vertical height from the eaves to the peak. The tool halves it, since a gable end is a triangle.

Frequently asked questions

What is a square of siding?: 100 square feet of finished wall. Siding, roofing and some cladding are all sold and quoted by the square, and a box of vinyl siding usually covers two of them.
How much siding waste should I allow?: Ten per cent for a simple rectangular house, 15 for one with a few dormers or angles, and up to 20 where there are many corners, gables or windows. The waste is offcuts, not breakage.
How do I measure a gable end for siding?: Take the width at the eaves and the vertical height to the peak, then halve the product. The tool does the halving when you mark the section as a gable.
Does the calculator include trim and corner posts?: It estimates the linear feet, adding the perimeter of every opening to the height of the outside corners. Order the profiles by that figure, allowing for the lengths your supplier stocks.
What is exposure and where do I find it?: The visible height of each course after the lap, and it is on the product's installation sheet. Vinyl usually quotes it in the profile name — a double-4 panel exposes two four-inch courses per piece.

Related tools

Square Footage Calculator — Calculate area in square feet or meters for rooms and projects, with cost.
Roofing Calculator — Estimate roof area, squares and shingle bundles from footprint and pitch.
Wallpaper Calculator — Rolls needed from wall size, roll size and pattern repeat, the way decorators count.
Paint Calculator — Work out how much paint a room needs from its size, coats, doors and windows.
Drywall Calculator — Estimate drywall sheets, joint compound, tape and screws for a room.
Stud Calculator — Count studs, plates, headers and cripples for a wall, openings included.