Calculators/Roofing squares

Roofing squares and bundles calculator

Footprint and pitch into real roof area, squares and bundles — because ordering against the footprint is how a roof ends up 12% short.

The roof

The flat plan area the roof covers, including overhangs. Not the sloped area — that is what this works out.

Three bundles per square covers most shingles, but heavier profiles run four or five. Check the wrapper.

The order

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Check the result against the job. This does the arithmetic from the values you enter. Building codes, span tables and material specifications vary by jurisdiction and by product, and the governing document is your approved drawings and your local code. Nothing you type here leaves your browser: the calculation runs on your device and we never receive it.

How this is checked. Every formula on this site runs from one shared calculation engine, and every one has a test fixture whose expected answer was worked out from the geometry or taken from a figure the trade already publishes — never from what the code returns. Some land exactly, which is the point: a 6/12 hip over a 144″ run is exactly 216″, a 45° crown in a square corner bevels at exactly 30°, and a 30° conduit bend has a multiplier of exactly 2. Where a number is a convention rather than arithmetic — a code limit, a waste allowance, bundles per square — it is an input with a stated default rather than a hidden constant. Found something wrong? Tell us at [email protected] and we will fix it and say so.

The footprint is not the roof

This is the single most expensive mistake in a roofing order. A roof covers more surface than the ground beneath it, and the multiplier is the slope factor for the pitch.

A 6/12 roof is 11.8% larger than its footprint. A 12/12 is 41% larger. Order against the footprint on a steep roof and you are not slightly short, you are a truckload short.

The full set of slope factors is in the pitch table.

Coming up short costs more than the material

A second delivery is the small part. Shingle bundles from a different production run can differ noticeably in shade, and on a roof anyone can see, a patch in the wrong tone is a callback rather than an inconvenience.

Which is why the waste allowance is not padding. Ten percent suits a simple gable; a cut-up roof with hips, valleys and dormers wants more, because every hip and valley turns full shingles into angled offcuts.

Field only. This counts the field of the roof. Starter course, ridge and hip cap, valley material, underlayment and flashing are separate line items and are measured in linear feet rather than squares.

Common questions

What is a roofing square?

One hundred square feet of roof surface. Roofing material is sold and quoted by the square rather than the square foot, and most three-tab and architectural shingles run three bundles to the square.

How do you convert a footprint to roof area?

Multiply the flat footprint by the slope factor for the pitch. A 6/12 roof has a slope factor of 1.118, so a 2,000 square foot footprint is about 2,236 square feet of actual roof. Ordering against the footprint leaves you 12 percent short.

How much waste should you allow for roofing?

Ten percent is a common starting point for a simple gable, and more for a cut-up roof with hips, valleys and dormers, because every hip and valley produces angled cuts and offcuts. Starter course and ridge cap are usually counted separately from the field.

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