Siding Calculator
Work out how much siding a house needs — wall area with openings deducted, boxes from your product's coverage, and wastage.
Siding is counted like paint — wall area minus openings — but bought by the box. This calculator does both: the area, then the boxes from your product's coverage.
Measure the house, count the openings, and enter the coverage from the packaging.
Your results
Enter your measurements and press Calculate.
Quantities are rounded up to whole tiles, planks, boxes or bags, after the wastage allowance. Cost appears only when you enter a price.
Formula
All lengths are converted to a single unit before the calculation: 1 ft = 0.3048 m, 1 in = 25.4 mm, 1 ft² = 0.09290304 m², 1 yd² = 9 ft². Material quantities are rounded up — you cannot buy part of a tile, plank or bag.
How to use this calculator
- Measure the house length, width and wall height.
- Count the doors and windows — they are deducted automatically.
- Enter the coverage per box from the product.
- Set wastage at 10% and add a price per box for a cost estimate.
Worked example
| House | 40 ft × 30 ft, 9 ft walls |
|---|---|
| Gross wall area | 2 × (40 + 30) × 9 = 1,260 ft² |
| Deductions | 2 doors (42 ft²) + 4 windows (60 ft²) = 102 ft² |
| Siding area | 1,260 − 102 = 1,158 ft² |
| Boxes (200 ft² each, 10% wastage) | ⌈(1,158 × 1.10) ÷ 200⌉ = 7 boxes |
Check it by hand: every step above uses the formula in the box. If your numbers match the example inputs but the calculator gives a different answer, please report it via the contact page.
Frequently asked questions
How much siding do I need?
The wall area minus doors and windows, divided by the coverage per box, plus 10% wastage. A 40 × 30 ft house with 9 ft walls needs 7 boxes of 200 ft². Enter your product's coverage above.
Do I deduct windows and doors from siding?
Yes — a door is about 21 ft² and a window about 15 ft² that you will not side. This calculator deducts them automatically; the figures are stated on the page.
What is siding coverage per box?
The area one box of siding covers, printed on the packaging — commonly 200 ft² (18.6 m²) per box. It varies by product, so enter your figure, not a guess.
Do I need extra for gables?
Yes — gable triangles are wall area too. Measure them as triangles (½ × base × height) and add the area to the wall area, or use the roof area calculator's sections as a guide. This calculator covers rectangular walls.
Related calculators
Estimates only. Results are for planning. Measure twice, confirm box coverage and tile sizes on the packaging you buy, and follow the manufacturer's instructions. See the disclaimer.