CALCULATION METHOD
How much siding do I need?
Multiply each rectangular wall’s width by height. Add triangular gables using one-half of base width times gable height. Subtract only the door and window area you intend to exclude, then add the selected waste allowance.
Wall area = wall length × wall height × matching walls
Gable area = ½ × gable width × gable height × matching gables
Order area = (wall area + gable area − openings) × (1 + waste)
One siding square = 100 sq ft
Siding calculator example
Four 40 × 10 ft wall sections plus two 40 × 8 ft triangular gables total 1,920 sq ft. After deducting 240 sq ft of large openings, the net area is 1,680 sq ft. Adding 10% waste gives 1,848 sq ft, or 18.48 siding squares.
Gable siding calculator: height or roof pitch
For a triangular gable, area is half the base width multiplied by the vertical height. If you know the roof pitch instead, use height = (base width ÷ 2) × (pitch rise ÷ 12) for a symmetrical gable. Use the measured-height option for a simple triangular gable whose peak is off-center. Break more complex shapes into measured sections.
Example: a 24 ft wide gable at 6:12 pitch has a 6 ft rise and 72 sq ft of area. Two matching gables total 144 sq ft. With no openings and 10% cutting allowance, you need 158.4 sq ft. To calculate only these gables, set the wall count to 0 and openings to 0.
Different wall sizes: a whole-house example
Add one group for two 40 × 10 ft walls and another for two 24 × 10 ft walls: 800 + 480 = 1,280 sq ft. Add two 24 ft gables at 6:12 pitch (144 sq ft), then deduct 160 sq ft of selected openings. Net area is 1,264 sq ft; with 10% allowance, required area is 1,390.4 sq ft. At 200 sq ft per carton, buy 7 full cartons covering 1,400 sq ft.
Vinyl siding calculator
Vinyl siding is commonly ordered by area or carton. Enter the actual coverage per panel and carton from the product label. The calculator rounds panels and cartons up, because partial packages may not be available.
Siding square footage calculator
A “square” is an ordering unit equal to 100 sq ft. The tool shows both exact square footage and squares, so you can compare supplier quotes that use different units.
House siding calculator with windows and doors
Industry measuring guidance often includes ordinary windows and doors as a built-in allowance for cuts. This tool lets you choose: enter zero to keep all openings included, or deduct only very large doors and windows when appropriate.
Siding cost calculator: required area versus purchase area
Choose price per carton, per square, or per square foot (per m² in metric mode). The worksheet separately shows the value of the required area and the budget for full cartons. For example, 1,390.4 sq ft at $0.90 per sq ft has a required-area value of $1,251.36, but 7 cartons covering 1,400 sq ft cost $1,260 at that rate. If a supplier sells loose pieces instead, ask for a piece-based quote. The total covers siding only; it excludes labor, delivery, tax, sheathing, housewrap, flashing, trim, soffit, fascia, fasteners, caulk, equipment, disposal, and permits.
Vinyl Siding Institute installation manual for rectangular and triangular area measurements, the 100 sq ft square, openings, starter strip, and waste planning; CertainTeed estimating guidance for wall and gable formulas and a 10% large-project waste allowance. Accessed September 11, 2026.