How much siding do I need for 120 ft of 9 ft walls?
For the worked example (120 ft of 9 ft walls plus 200 sq ft of gables) the material list is Siding: 15 squares (calculated 14.08 squares, based on 10% extra). Quantities to buy are whole units rounded up from the calculated amounts. Enter your own measurements in the calculator above for your exact list.
How to use this calculator
- Enter the total wall length and height, or the wall area if you already know it.
- Add gable and other area. Subtract only large openings, such as a garage door: ordinary windows and doors are usually left in.
- Choose whether your siding is sold by the square or by the carton. For cartons, enter the installed coverage on the carton.
- Copy, print or share the material list.
How this is calculated
- Net siding area = wall area + gables and other area − large openings
- With allowance = net area × (1 + allowance ÷ 100)
- Squares = round up (with allowance ÷ 100 sq ft)
- Cartons = round up (with allowance ÷ coverage per carton)
Geometry is deterministic. Material coverage, density, installation waste and product yield can vary. We expose those assumptions so you can replace them with the values printed on the products you are actually buying. Treat every result as an estimate. Items on your list are labelled Calculated (straight from your measurements) or Estimated (depends on an assumption), and “Buy” quantities are whole units rounded up.
Sources
- Polymeric Exteriors (Vinyl Siding Institute) – How to Install Vinyl Siding: Estimating Required Materials. Every 100 square feet (9.29 square meters) is called a “square” for ordering purposes; windows and doors are not usually deducted, and very large openings can be. Used for the 100 sq ft square. Carton coverage is entered by you.
Last reviewed: . See the methodology.
Assumptions
These starting values are used until you change them. They are typical, not universal. Check the label on the product you are buying.
| Assumption | Starting value | Where it comes from |
|---|---|---|
| Siding square | 100 sq ft | Manufacturer / industry sourced – Siding is ordered by the square: every 100 sq ft is one square (Polymeric Exteriors installation manual). |
| Extra allowance | 10% | Common planning default |
| Installed coverage per carton | You enter it | You enter it (product / supplier) |
Worked example
A 120 ft run of 9 ft walls plus 200 sq ft of gables, with 10% extra:
- Siding: 15 squares (1,408 sq ft including the allowance) · 10% extra
Common questions
What is a siding square?
Siding is ordered by the square, and every 100 sq ft is one square. The calculator rounds up to whole squares, or to whole cartons if you enter a carton’s coverage.
Should I subtract windows and doors?
It is up to you. The vinyl siding installation manual we cite says windows and doors are not usually deducted, because including them builds in a waste allowance, and that very large openings can be deducted. Subtracting gives a tighter number.
Does it count trim and corners?
No. J-channel, starter strip, corner posts, soffit and fascia are measured in linear feet and are listed as reminders only.
Guides
- How Much Siding Do I Need?Wall and gable area, large openings, allowance, then squares or cartons.
- What Is a Square of Siding?100 sq ft: the siding ordering unit, and how it differs from area and cartons.
- How Many Bundles of Shingles Do I Need?Roof area plus allowance, divided by one bundle's coverage, rounded up.
- What Is a Roofing Square?100 sq ft of roof surface, and how pitch and product turn squares into bundles.