How much siding do I need?

Add up the wall area by multiplying the home's perimeter by the wall height, subtract the door and window openings, then add about 10 percent for waste. Divide by 100 to get siding squares — a square covers 100 square feet. A 140 ft perimeter at 9 ft tall with a few openings works out to about 13 squares.

How much waste should I add for siding?

Add about 10 percent for a simple, boxy house, and 15 percent or more for homes with lots of corners, gables, and windows, which create more cut-off waste. Steeper gables and intricate trim push the figure higher.

Siding Calculator — How Much Vinyl Siding?

Q: What is a square of siding?

A square is 100 square feet of wall coverage — the unit siding is measured and sold in. Most vinyl siding comes in boxes that cover two squares (200 square feet), so divide your squares by two to get boxes.

Q: Do I subtract windows and doors?

Yes. Subtract large openings like windows, doors, and garage doors so you don't pay for siding you won't install. This calculator subtracts about 15 square feet per window and 21 per door; adjust if yours are larger.

How to calculate siding

Siding is estimated from the net wall area, then converted to squares:

Wall area = perimeter × height − openings, then squares = area × (1 + waste) ÷ 100

The perimeter is the sum of all the walls you're siding; multiply by the average wall height for gross area, then subtract roughly 21 sq ft per door and 15 per window. Add a waste allowance for cuts around corners and openings, divide by 100 to get squares, and round up. Triangular gable ends should be added on top (base × height ÷ 2 each).

Siding by the numbers

Unit	Covers
1 square	100 sq ft of wall
1 box of vinyl (typical)	2 squares / 200 sq ft
Simple boxy house	~10% waste
Many corners & gables	~15%+ waste

Siding materials compared

Vinyl is the most common, but the material sets the cost, look, and upkeep:

Material	Relative cost	Lifespan	Upkeep
Vinyl	$ (lowest)	20–40 yrs	Wash only
Engineered wood	$$	20–30 yrs	Repaint periodically
Aluminum	$$	30–40 yrs	Low; can dent
Fiber cement (e.g. Hardie)	$$$	30–50 yrs	Repaint ~10–15 yrs
Cedar / wood	$$$	20–40 yrs	Stain/seal regularly
Brick / stone veneer	$$$$	50+ yrs	Almost none

Weighing two popular options? See our guide on vinyl vs. fiber-cement siding.

Don't forget trim and accessories

Trim pieces. J-channel, corner posts, starter strip, and soffit/fascia are bought separately from the field siding.
House wrap. A weather-resistive barrier goes on before the siding — sized by the same wall area.
Gables add up. Each triangular gable is base × height ÷ 2 — add them to your wall area.
Order one dye lot. Buy all the siding together so the color matches across boxes.

How much does siding cost?

Material runs about $100–$300 per square (100 sq ft) — vinyl at the low end, fiber cement and wood higher, brick or stone veneer the most. Installed, expect roughly $4–$12 per square foot with labor, depending on material and house complexity.

DIY or hire a pro?

Vinyl siding is one of the more DIY-friendly exterior jobs on a single-story home — the panels are light and snap together over house wrap, and the main costs are time and a few special tools (a snap-lock punch, a zip tool, and tin snips). Fiber cement is a different story: the boards are heavy, throw silica dust that needs a proper mask and shears or a dust-collecting saw, and really want two people. And any two-story wall means scaffolding or staging and the safety that comes with it. For a tall, complex, or fiber-cement house a pro crew is usually worth it; a one-story vinyl re-side is a realistic weekend-plus project for a confident DIYer.

Frequently asked questions

What is a square of siding?

100 sq ft of wall coverage. Siding is measured and sold in squares; most vinyl boxes cover 2 squares (200 sq ft).

How many boxes of vinyl siding?

Divide your squares by 2 — a typical vinyl box covers about 2 squares. The calculator shows both.

How much waste should I add?

About 10% for a simple house, 15% or more for lots of corners, gables, and windows.

Do I subtract windows and doors?

Yes — large openings come out of the area. We use ~15 sq ft per window and ~21 per door; adjust for bigger ones.

What's the cheapest siding?

Vinyl is the lowest cost and lowest maintenance, which is why it's on most homes. Engineered wood and aluminum are the next step up.

Vinyl or fiber cement?

Vinyl is cheaper and never needs painting; fiber cement costs more but is more durable and impact-resistant. See our vinyl vs. fiber-cement guide for the full comparison.

Do I need house wrap under siding?

Yes — a weather-resistive barrier (house wrap) goes over the sheathing before siding to manage moisture and air. Size it by the same wall area.

Can I install siding myself?

Single-story vinyl is realistic for a confident DIYer with a few special tools. Fiber cement is heavy and dusty (and two-person work), and any two-story wall needs scaffolding — those are better left to a pro.

Can you put new siding over old?

Sometimes — vinyl can go over flat, sound wood siding with furring strips, but it hides what's underneath. Removing the old siding lets you inspect and wrap the sheathing, which is the better long-term job.