Roofing Calculator
Square feet, shingle bundles or panels, underlayment and trim.
| Order item | Whole units | Cost |
|---|---|---|
| Roofing packs / bundles | 50 packs | — |
| Underlayment rolls | 5 pcs | — |
| Ridge and hip units | 2 pcs | — |
| Edge / drip-edge pieces | 18 pcs | — |
How it works
Overhangs are added to the rectangular building plan before the pitch factor is applied. Roof area equals horizontal plan area divided by cosine of the pitch. A gable has two rectangular planes, a shed has one, and a hip roof uses the same uniform-pitch area factor with its ridge and four hips calculated separately.
Coverage products divide allowance-adjusted area by the effective area on one bundle, pack or roll. Rectangular gable and shed planes count panel columns and rows from effective dimensions; hip panels fall back to area because their cuts need a layout. Underlayment, ridge/hip units and edge pieces use their own effective coverages.
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How the Roofing Calculator works
This US roofing calculator converts building dimensions in feet, overhangs and either degrees or X:12 pitch into sloped square footage. It estimates shingle bundles or effective-size panels, underlayment rolls, ridge and hip products, drip edge and optional material cost.
Pitch changes square footage
The roof plan includes overhangs on both ends and both eave sides. Sloped area is horizontal plan area multiplied by the pitch factor: a 6:12 roof uses √1.25, or about 1.118. That is why ordering from the house footprint alone comes up short.
Gable and shed roofs have rectangular planes. A uniform-pitch hip roof uses the same area factor, while its ridge and four hip lengths are calculated separately for cap products.
Bundles, roofing squares and panels
One roofing square is 100 sq ft, but shingles are purchased in bundles whose effective coverage belongs in the form. The editable 33.3 sq ft default represents a common three-bundle-per-square planning value; use the exact wrapper coverage for the selected product.
Panel mode rounds rectangular planes to complete columns and rows using effective width and length after laps. Hip-roof sheets are area-based because triangles, trapezoids and reusable offcuts require a cutting layout.
Keep accessory rounding visible
Underlayment uses effective square feet per roll, ridge and hip products use effective linear feet per pack or piece, and drip edge uses usable stock length. Each item rounds independently and can carry its own unit price.
The estimate excludes structural framing, roof deck replacement, ice barriers outside the entered underlayment, ventilation, flashing assemblies, penetrations, fasteners, delivery, labor and tax.
FAQ
How many bundles cover a 40 × 30 ft gable roof? expand_more
With 1 ft overhangs on every side and a 6:12 pitch, the plan is 42 × 32 ft and the sloped area is about 1,502.64 sq ft. A 10% allowance raises the order area to about 1,652.90 sq ft. At 33.3 sq ft per bundle, round up to 50 bundles.
How many roofing squares is that roof? expand_more
The net sloped area is about 15.03 squares, while the ten-percent order area is about 16.53 squares. Bundles still round from their exact effective coverage rather than from a rounded square count.
How is a 6:12 pitch converted? expand_more
Rise divided by run is 6 ÷ 12 = 0.5. The angle is arctan(0.5), about 26.6°, and the slope factor is √(1 + 0.5²), about 1.118.
Does the calculator include valleys and dormers? expand_more
No. It models one rectangular gable, shed or hip roof. Measure additional planes separately and make a roof-specific cutting and flashing schedule before ordering.