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Roofing calculator: squares, bundles and pitch

Work out how much roofing a house or building needs. Enter the footprint including overhangs and the pitch, and get the true roof area, the squares to order with waste, the shingle bundles and the underlayment — with the pitch factor shown.

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Tool 12

Roofing: squares, bundles & underlayment

Enter the footprint of the roof including overhangs and its pitch, and get the true roof area, the roofing squares with waste, shingle bundles, underlayment rolls and the material cost.

The roof

Result

Pitch factor = √(1 + (rise ÷ 12)²): 1.118 at 6/12. Roof area = footprint × pitch factor — this holds for gable and hip roofs of one pitch. Squares = roof area ÷ 100, then × (1 + waste %). Bundles = squares × bundles per square, rounded up. Underlayment assumes synthetic rolls of 10 squares (1,000 sq ft); #15 felt rolls cover about 4 squares.

How to use it

  1. Measure the footprint length and width, including the overhangs.
  2. Choose the pitch — the rise in inches per 12 inches of run.
  3. Enter waste: about 10% on a simple gable, 15% or more with hips, valleys and dormers.
  4. Enter bundles per square and your price per square, and read the order.

A worked example

A 50 × 32 ft footprint is 1,600 sq ft. At a 6/12 pitch the pitch factor is 1.118, so the roof is 1,789 sq ft — 17.9 squares. With 10% waste, order 19.7 squares: 60 bundles at three per square, two rolls of synthetic underlayment, about $2,660 of shingles at $135 a square.
Quantities are half the job. The trade guide covers what to track once the material is ordered — unit costs, waste against the estimate, and the software that shows them.
Read: Software for roofing contractors →

Questions

How do you calculate roofing squares?

One roofing square is 100 sq ft of roof surface. Multiply the footprint area by the pitch factor to get the roof area, divide by 100, and add waste.

What is the pitch factor for a 6/12 roof?

1.118 — the square root of 1 + (6 ÷ 12)². A 4/12 roof is 1.054, 8/12 is 1.202, 10/12 is 1.302 and 12/12 is 1.414.

How many bundles of shingles are in a square?

Three for most architectural and 3-tab shingles; some heavier designer shingles take four or five. Check the wrapper.

How much waste should I add for roofing?

About 10% on a simple gable roof and 15% or more on hip roofs and cut-up roofs with valleys and dormers. Ridge cap and starter strip are ordered separately by the linear foot.

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Want this on your live data, every morning?

These tools are manual. The dashboard does the same arithmetic across every job, every company and every week — plus the money-at-risk view, the audit findings and the overrun radar. Join the private beta and we will connect it to the systems you already run.