Vinyl siding is priced by the “square” – 100 ft² of wall – and usually packed two squares to a box. Besides the panels you need starter strip along the bottom, J-channel around windows and doors, undersill trim beneath windows and at the top of walls, and inside and outside corner posts.
How to use the Vinyl Siding Calculator
- House perimeter
- Wall height
- Gable ends
- Gable width
- Gable height
- Doors (3 × 7 ft)
- Windows (3 × 5 ft)
- Outside corners
- Waste
- Price per square (100 ft²)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the house perimeter and wall height, the number and size of gables, the number of doors, windows and outside corners, waste and price per square. The calculator works out the net wall area, squares and boxes and all the trim lengths.
Tips for an accurate estimate
- Sketch the job and split irregular areas into rectangles, circles and triangles before you measure.
- Add a waste allowance – typically 5–10% for simple layouts and 15–20% for diagonal, curved or heavily cut work.
- Check the coverage or yield printed on the product, because sizes and densities vary between manufacturers.
- Buy all units of a finished material (tile, brick, siding) from the same batch so colours match, and keep a few spares for repairs.
- Confirm local prices – quarry, lumber and steel prices vary widely by region and season.
Common mistakes to avoid
- Ordering exactly the calculated amount with no allowance for breakage, offcuts and settlement.
- Forgetting to subtract doors, windows and other openings – or subtracting small ones that still need cutting around.
- Confusing US short tons (2,000 lb) with metric tonnes (1,000 kg) when comparing quotes.
Inputs explained
| Field | What to enter |
|---|---|
| House perimeter | Units: ft, m, in, yd, cm |
| Wall height | Units: ft, m, in, yd, cm |
| Gable ends | A number |
| Gable width | Units: ft, m, in, yd, cm |
| Gable height | Units: ft, m, in, yd, cm |
| Doors (3 × 7 ft) | A number |
| Windows (3 × 5 ft) | A number |
| Outside corners | A number |
| Waste | In % |
| Price per square (100 ft²) | Units: /square |
What each result means
- Net siding area = max([House perimeter]×[Wall height] + [Gable ends]×[Gable width]×[Gable height]÷2 – [Doors (3 × 7 ft)]×1.9509638400000002 – [Windows (3 × 5 ft)]×1.3935456000000002, 0)
- Squares to buy = ceil([Net siding area]×(1 + [Waste]÷100)÷9.290304)
- Boxes (2 squares each) = ceil([Squares to buy]÷2)
- J-channel = [Windows (3 × 5 ft)]×16×0.3048 + [Doors (3 × 7 ft)]×17×0.3048 + [Gable ends]×sqrt([Gable width]^2÷4 + [Gable height]^2)×2
- Undersill trim = [Windows (3 × 5 ft)]×3×0.3048 + [House perimeter]
- Outside corner posts (10 ft) = [Outside corners]×ceil([Wall height]÷3.048 – 0.000001)
- Siding cost = [Squares to buy]×[Price per square (100 ft²)]
Example values
How the main result changes when House perimeter changes and everything else stays at the example values above:
| House perimeter (ft) | Squares to buy |
|---|---|
| 80 | 9 |
| 120 | 13 |
| 160 | 17 |
| 200 | 20 |
| 240 | 24 |
| 320 | 32 |
Formula
Wall area = perimeter × height + gables × width × height ÷ 2 − doors − windowsSquares = area × (1 + waste) ÷ 100 ft²J-channel ≈ 16 ft per window + 17 ft per door; starter = perimeterWorked example
Inputs — House perimeter: 160 ft; Wall height: 9 ft; Gable ends: 2; Gable width: 30 ft; Gable height: 8 ft; Doors (3 × 7 ft): 2; Windows (3 × 5 ft): 12; Outside corners: 4; Waste: 10 %; Price per square (100 ft²): $120 /square.
Results — Net siding area = 1,458 ft²; Squares to buy = 17; Boxes (2 squares each) = 9; Starter strip = 160 ft; J-channel = 294 ft; Undersill trim = 196 ft; Outside corner posts (10 ft) = 4; Siding cost = $2,040.00.
Key terms
- Square
- 100 ft² (9.29 m²) of wall coverage.
Frequently asked questions
How many squares of siding do I need?
Divide the net wall area by 100 and add 10% – a 2,000 ft² wall area needs 22 squares.
How much J-channel per window?
About 16 ft for a typical 3 × 5 ft window (around all four sides).
How much does vinyl siding weigh?
About 40–50 lb per square – light enough for one person to handle.
What formula does the Vinyl Siding Calculator use?
Wall area = perimeter × height + gables × width × height ÷ 2 − doors − windows.