Siding Square Calculator — Convert Sq Ft, Squares, Cartons, Linear Ft & Bd Ft

What Is a Siding Square, Exactly?

A square is the industry's standard unit for exterior cladding — siding, roofing, shingles, even decking. One square equals 100 square feet of installed coverage. But it was not always this way. The square was born in 19th-century roofing, where bundles of cedar shingles were counted by how much roof they would cover (100 sq ft per bundle). Siding adopted the same unit because every trade on a residential exterior uses squares — roofer, siding installer, painter, and drywaller all speak the same language.

Why not just square feet? Because ordering in hundreds is clumsy. A 2,000 sq ft house is 20 squares — easier to quote, easier to order, easier to stack on a truck. The unit also normalizes profiles that cover very different wall areas per carton. A vinyl D4 carton covers 2 squares; a board-and-batten carton covers roughly 1.2 squares; metal standing seam covers about 2.4 squares. Squares put them all on one number line.

📦Squares are the unit on the delivery truck, the invoice, and the quote

Squares are the unit on the delivery truck, the invoice, and the quotePhoto: Unsplash

Quick conversions to memorize

1 square =100 sq ft

1 square ≈2 vinyl cartons

1 square ≈1.5 Hardie cartons

1 square @ 6″ exp ≈267 linear ft

1 square @ 4″ exp ≈300 linear ft

Every Conversion Formula, One Place

The converter above runs these formulas live. Bookmark this section for when you're at the supply counter and need to convert without a calculator.