How many square feet are in a square of siding?

Exactly 100 square feet. So squares = area ÷ 100, rounded up: 1,336 sq ft is 14 squares of bare coverage, or 15 squares with a 10% waste factor.

How many boxes of vinyl siding are in a square?

Double-4″ and double-5″ vinyl typically cover about 200 sq ft per box, which is 2 squares per box — so one square is half a box, and 16 squares is 8 boxes. Confirm the coverage on your box label.

How many bundles of cedar shingles are in a square?

At a ~5″ exposure, cedar shingles cover about 25 sq ft per bundle, so roughly 4 bundles make a square. A tighter exposure needs more bundles per square.

What is a “square” of siding? (and how many you need)

Q: What is a square of siding?

A square is 100 square feet of installed siding coverage. It is a unit of area, borrowed from roofing, that the trade uses to size jobs and price material and labor regardless of the product.

Contractors quote siding by the “square,” not the square foot or the box. The unit is simple — 100 sq ft of coverage — but understanding why it exists makes every quote and every material order easier to read.

By Francesco Zinghinì

The definition

One square of siding = 100 square feet of installed coverage. That is the whole definition. It is a unit of area covered, borrowed from roofing, and it exists because 100 is a convenient round number to price labor and material against. When a contractor says a job is “16 squares” they mean 1,600 sq ft of wall to cover; when they quote “$700 a square” they are pricing each 100 sq ft of finished siding, material and labor bundled.

Why the trade uses squares

Two reasons, both practical. First, it collapses the difference between products: a box of vinyl, a bundle of shingles and a carton of fiber-cement plank all cover a different raw area, but all convert cleanly to squares, so a crew can talk about a job’s size and a day’s output in one unit regardless of material. Second, it makes labor pricing legible — “we hang about X squares a day” is a schedule; “we hang about X square feet a day” is the same fact in noisier digits. The square is the common denominator of the trade.

Converting your area to squares

The conversion is a division and a ceiling:

squares = ceil( area ÷ 100 ), or with waste, ceil( area × (1 + waste%) ÷ 100 )

1,336 sq ft of net area is 13.36 squares of coverage, which rounds up to 14 squares of bare material; add a 10% waste factor and it is ceil(1,469.6 ÷ 100) = 15 squares to actually buy. The bare-vs-with-waste distinction matters when you read a quote: a contractor pricing “by the square” usually means installed squares of coverage, and their own waste is inside their unit price — so compare their square count to your net squares (14), not your purchased squares (15). The siding squares calculator does both.

Squares, boxes and bundles are not the same thing

A square is a unit of coverage; a box or bundle is a unit of packaging. They only line up if you know the product’s coverage:

Vinyl lap (double-4″ or double-5″) — about 200 sq ft per box, i.e. 2 squares per box. Sixteen squares is 8 boxes.
Cedar shingles/shakes — about 25 sq ft per bundle at a ~5″ exposure, i.e. 4 bundles ≈ 1 square. Sixteen squares is roughly 64 bundles, before waste.
Fiber cement, engineered wood, wood bevel — usually sold by the piece or the square; the pieces-per-square depend on the plank length and the exposure.

The exact coverage is on the manufacturer’s label. Our coverage-by-material table holds the typicals as a planning snapshot, and the boxes-by-material calculator turns your area straight into boxes or bundles: units = ceil(area × (1 + waste) ÷ coverage).

How exposure changes the count

For shingles and shakes especially, the exposure — the visible height of each course — controls coverage. A cedar shingle rated for ~25 sq ft/bundle at a 5″ exposure covers less if you set it to a 4″ exposure for a tighter look, because more courses fit the same wall and each course consumes more material. Halving the exposure roughly doubles the bundle count. This is why the manufacturer states coverage at a given exposure, and why copying a bundle count from a different exposure is a classic over- or under-order. The exposure reference lists the typical reveals by material.

Pricing by the square

Because the square is a coverage unit, it also drives cost. If you know your square count and a quoted price per square, the job total is squares × $/square + add-ons, ×(1 + contingency). Fifteen squares at $700/square is $10,500 before add-ons; the cost-by-squares calculator handles it. Two cautions: a “per square” price may or may not include tear-off, trim and accessories, and a low per-square number often means a thinner product or a labor-only figure. Read the quote for what is inside the square before comparing two of them.

Squares as a schedule, not just a quantity

Because a square is a fixed 100 sq ft, it doubles as a unit of time. A crew that hangs, say, a handful of squares of lap a day turns a square count directly into a rough schedule: a 15-square house is a few days of hanging before trim and detail work. Heavier or more intricate materials move fewer squares per day — fiber cement and hand-set shakes are slower than light vinyl lap — so the same square count is a longer job in a denser product. This is why a contractor who quotes in squares can also tell you the duration from the same number, and why comparing two quotes on squares-per-day reveals as much about the crew’s pace as the price does. When you read your own square count, read it twice: once as material to buy, once as days to schedule.

The short version

A square is 100 sq ft of coverage; you buy ceil(area ÷ 100) squares of bare material and a little more for waste; and you translate squares into boxes or bundles with the product’s coverage, at the exposure you are actually installing. Keep those three ideas straight and neither the order desk nor the estimate will surprise you.