Enter the total length and height of the walls and the size of the gables. The calculator gives the squares of siding to order, the cartons if you know the coverage, the starter strip and the fasteners.
How to use the siding calculator
- Add up the length of every wall you will side. For a whole rectangular house that is the perimeter.
- Enter the wall height from the bottom of the siding to the eaves.
- Enter the number of gables and the width and height of one gable. For gables of different sizes, run the calculator for each and add the results.
- Deduct only large openings such as garage and patio doors, and keep a waste allowance.
Siding formulas
Wall area = total wall length × wall height Gable area = ½ × gable width × gable height, for each gable Net area = walls + gables − large openings Squares = net area × (1 + waste %) ÷ 100
The Polymeric Exterior Products Association’s installation manual uses these same formulas and calls each 100 ft² a square. It notes that windows and doors are not usually deducted, because leaving them in gives an allowance for waste; only very large openings come off. Fasteners are estimated at 0.01 lb per ft² for roofing nails, staples or screws, or 0.005 lb per ft² for aluminum nails, and the starter strip runs the length of the base of the walls.
Worked example: a 40 × 30 ft house, 9 ft walls, two gables
- Walls: 140 ft of perimeter × 9 ft = 1,260 ft².
- Gables: 2 × ½ × 30 × 8 = 240 ft².
- Net area: 1,500 ft². With 10% waste: 1,650 ft².
- Siding to order: 16.5 squares, plus 140 ft of starter strip and about 15 lb of roofing nails.
How much siding is in a box?
It depends on the product and the profile, so read the carton: the coverage is printed on it in square feet or squares. Enter it in the calculator to get the carton count. Trim pieces such as J-channel, corners and soffit are sold by the piece and measured separately.
Tips for estimating siding
- Measure each wall at its widest point. Bump-outs and bays add length; measure around them.
- Add more waste for complex houses. Many corners, dormers and steep gables mean more cut pieces.
- Order trim from the same run. Colour can shift between production batches.
- Doing the eaves too? Use the soffit calculator for soffit and fascia.
Questions
How many squares of siding do I need for a 2,000 sq ft house?
Floor area does not tell you the wall area. Measure the perimeter and wall height: a two-storey house with a 40 × 25 ft footprint and 18 ft walls has 130 × 18 = 2,340 ft² of wall before gables.
Do I subtract windows and doors?
Usually not. Leaving them in covers the waste from cutting around them. Subtract garage doors and large sliding doors.
What is a square of siding?
100 ft² of wall coverage.
How do I calculate a gable?
Half the width times the height from the eave line to the peak.
Sources
- Vinyl Siding Installation Manual: Getting Started, Polymeric Exterior Products Association.
Used for: Square = 100 ft², wall and gable formulas, not deducting windows and doors, starter strip and fastener estimates. - NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
Used for: Exact inch and foot definitions.