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Roofing Calculator

Roof area, squares and bundles from pitch and footprint.

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Materials

ItemCoverageQuantity

Pitch multipliers

A pitched roof covers more surface than the ground beneath it — this is the step most estimates miss.

PitchMultiplierAngleExtra area

Roofing squares

—

Areas

Footprint area—
Actual roof area—
With waste—
Shingle bundles—

—

Estimated material cost at your rate

A roofing square is 100 square feet, the unit the trade quotes in. Three bundles of standard architectural shingles cover one square; heavier premium shingles can need four, so check the wrapper before ordering.

Quick Tool Overview

The Roofing Calculator estimates a job from the building footprint and roof pitch, applying the pitch multiplier that turns ground area into actual roof surface, then converting that into squares, shingle bundles, underlayment and nails.

What it does
Calculates roof area and the materials to cover it
You give it
Building footprint, roof pitch and a waste allowance
You get back
Squares, bundles, underlayment, ridge cap and nails
Best for
Re-roofing estimates and comparing contractor quotes
Calculators Free, unlimited use No sign-up Runs in your browser

About the Roofing Calculator

Estimate a roofing job from the building footprint and the pitch. Because a pitched roof covers more surface than the ground beneath it, the footprint is multiplied by a pitch factor, and the result is converted into roofing squares, bundles, underlayment and nails.

That pitch factor is what people leave out. A 6/12 roof has about 12 percent more surface than its footprint, and a steep 12/12 roof has 41 percent more — order from the footprint alone and you will be short by a very expensive margin. A roofing square is 100 square feet and is the unit the trade quotes in, with three bundles of standard architectural shingles covering one.

Key features of the Roofing Calculator

Pitch multiplier applied

A 12/12 roof has 41 percent more surface than its footprint — the step most DIY estimates leave out entirely.

Quoted in squares

The trade unit of 100 square feet, so your figure is directly comparable to a contractor quote.

Full material list

Shingle bundles, underlayment rolls, ridge cap and nails, not just an area.

Waste by roof complexity

10 percent for a simple gable, 15 or more once hips, valleys and dormers are involved.

Pitch table included

Common pitches with their multipliers and angles, for when you are estimating the slope by eye.

How to use the Roofing Calculator

  1. 1

    Measure the footprint

    Length and width of the building at ground level, including overhangs.

  2. 2

    Enter the pitch

    As rise over run, such as 6/12. The multiplier for that pitch is shown.

  3. 3

    Add waste

    10 percent for a simple gable; 15 or more for hips, valleys and dormers.

  4. 4

    Read the materials

    Squares, shingle bundles, underlayment rolls, ridge cap and nails.

Frequently asked questions

100 square feet of roof surface. It is the unit roofers quote in, so a 2,000 square foot roof is 20 squares.

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