What is a roof square?

One hundred square feet

A roofing square is exactly 100 square feet of roof surface — a ten-by-ten patch. It is not a unit of area anyone else uses, and that is the point: it is sized so that a square of standard shingles is 3 bundles, roughly what one roofer carries up a ladder in three trips. Everything downstream is quoted against it.

Squares to bundles to dollars

The whole takeoff is one chain. Footprint × pitch multiplier gives roof surface; surface ÷ 100 gives squares; squares × 3 gives bundles; squares × the installed rate gives the price. A twenty-square asphalt roof is sixty bundles and, at $475 to $1,875 a square installed, somewhere between $9,500 and $37,500 of covering.

Break the chain anywhere and the number is wrong everywhere after it. The square calculator and the bundle calculator run the two halves of it.

Squares are slope area, not floor area

The most expensive mistake in a self-measured takeoff is counting the footprint as the roof. A 1,700 sq ft plan is seventeen squares of floor and 19.0 squares of roof at 6/12 — 11.8% more. At 10/12 it is 22.1 squares. The correction is the pitch multiplier, and it applies before anything else.

Ordered squares and net squares

There are two square counts on every job and they are never the same. Net squares is the surface you are covering. Ordered squares is net plus waste — 10% for a plain gable, 15% for hips and valleys, 18% or more for a cut-up roof. Waste pays for the starter cut from full shingles, the cap cut from field shingles, the valley cuts and the offcuts at every rake. A bid quoting net squares and a bid quoting ordered squares will look 15% apart on paper and be identical in reality.

Reading a per-square quote

When a contractor says “six hundred a square”, ask two questions: how many squares, and net or ordered. Those two answers turn a rate into a price, and they are the two most common places for a bid to be quietly different from its neighbour. Once you have both, the cost calculator will tell you whether the rate is in the national band, and the replacement cost guide explains what belongs inside it.