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Home Roofing calculator

Roofing Calculator in 3D

Start with the building footprint and roof pitch. See the actual sloping area, compare roof forms, and turn that area into roofing squares and shingle bundles. Separate the roof planes to see exactly what is being measured.

Explore This Calculator

Outside wall to outside wall.

Span across the building.

Same extension on all sides.

All planes use this pitch.

Complete gable roof on a simple house, with two contrasting pitched planes and visible eavesDrag to Rotate

Roof dimensions include the horizontal overhang. The wall footprint stays visible below.

This calculator covers one rectangular building with a uniform-pitch gable, hip, or single-slope roof. It estimates surface quantities. Dormers, valleys, openings, additions, structural member sizing, and installation requirements need separate assessment.

Every Roof Plane Counts

A roof’s sloping faces cover more area than their horizontal projection. Select a plane below to highlight it in the 3D model, or separate the planes to see how their areas add up.

Actual surface area by roof plane
Roof Plane Surface Area Inspect
Front Plane 751.32 ft²
Back Plane 751.32 ft²
Total Roof Area 1,502.64 ft²
Default gable roof planes separated to expose both complete sloping surfaces
Default gable example. Use the model above for your current roof.

Turn Pitch Into Real Surface Area

Pitch is vertical rise for every 12 units of horizontal run. The slope multiplier converts horizontal roof plan area into actual surface area. The geometry uses the same pitch on every roof plane.

Roof pitch section Pitch 6:12 · 26.57° · Multiplier 1.118 Run 16 ft Rise 8 ft Roof-edge dimensions include horizontal overhang. Slope length: 17.89 ft.

Changing the angle also changes the pitch and model.

Horizontal run
16 ft
Vertical rise
8 ft
Slope length
17.89 ft
Slope multiplierm = √(1 + (pitch / 12)²)
Actual roof areaA = Lroof × Wroof × m
Roofing squaresS = area in ft² / 100

The slope length includes the horizontal overhang and describes an edge-to-ridge path, or low-to-high edge for a single slope. It is not a cut-ready rafter length; ridge thickness, seat cuts, and connections are additional.

From Roof Area to an Order Quantity

First measure the roof surface. Then apply your chosen waste percentage. Finally round the package count up to whole bundles. Waste is applied once, before rounding.

Measured Roof1,502.64 ft²

15.03 squares before waste

With Your Allowance1,652.9 ft²

Add 150.26 ft² for waste

Whole Bundles50

Package coverage: 1,666.67 ft²

These are field-shingle quantities. Starter strips, hip and ridge caps, underlayment, flashing, fasteners, and ventilation components are separate. A roof area can also inform a metal-roof estimate, but panel counts require the product’s effective coverage, laps, and cut layout.

Measure the Edges Too

Eaves are horizontal roof edges. Rakes are sloping outer edges. A gable has a ridge; a hip roof also has four diagonal hips. A single-slope roof has a separate high edge.

Lengths describe this roof’s geometry. They do not include overlaps, laps, trim waste, or attachment allowances.

Eaves
84 ft
Rakes
71.55 ft
Ridge
42 ft
Hips, combined
0 ft
High edge
0 ft
Outer perimeter
155.55 ft

Your Rates. Your Estimate.

Enter the bundle price and a labor rate for this job. Materials use the rounded bundle quantity; labor uses the actual roof area before material waste. No regional price is assumed.

Field-shingle materials
Enter Price
Area-based labor
Enter Rate
Entered-Rate Subtotal
Enter Rates

Subtotal excludes unspecified items such as tear-off, disposal, repairs, accessories, delivery, taxes, and permits. A zero rate contributes zero to a subtotal once another rate is entered.

Roofing Calculation Questions

Why is roof area larger than the building footprint?

Overhangs extend the roof past the walls, and pitch tilts each face. The calculator adds the horizontal overhang first, then multiplies that plan area by the slope multiplier.

Do equal-pitch gable and hip roofs have the same total area?

For the same rectangular roof outline and uniform pitch, yes. Their horizontal projections cover the same area and every face has the same slope multiplier. The number of faces, hip lengths, and practical cutting waste differ.

Is one roofing square the same as one bundle?

A roofing square covers 100 square feet. A bundle is a product package. The number of bundles covering a square depends on the product; enter the coverage specified by its manufacturer.

Can I use a zero pitch?

Zero pitch gives a horizontal surface for area comparison. It does not mean a roofing product is suitable for that slope. Product slope limits, drainage, and installation details must be checked separately.