Measure the footprint
Multiply length by width for the horizontal footprint, not the sloped surface. Split irregular plans into rectangles.
Tool Switcher: Roofing
Project toolsTools
Roofing planning tool
Roofing Calculator
Turn a roof footprint and pitch into whole shingle bundles, plus the underlayment, ridge cap, and drip edge underneath.
- Pitch-adjusted area
- US and metric units
- Full material ticket
Roofing planning tool
Roofing Calculator
Estimate shingle bundles, underlayment, ridge cap, and drip edge.
Methodology
From footprint and pitch to a material ticket
Apply the pitch factor
The pitch factor converts footprint to true sloped surface: the square root of one plus the pitch squared.
Convert to squares
Roofing is sold in squares of 100 square feet. Divide the sloped area, add the waste allowance, then round up whole bundles.
Count bundles and accessories
Underlayment, ridge cap, and drip edge scale off the roof area, ridge length, and perimeter respectively.
Worked example
A 30 × 40 ft ranch at 6/12 pitch
1,341.64 ft²sloped roof surface
÷100square feet per square
=14.76 squares45 bundles
A 30 × 40 ft footprint at 6/12 pitch gives about 1,341.64 ft² of roof surface, or 14.76 squares with a 10% allowance. That means 45 bundles of shingles, 4 rolls of underlayment, 2 bundles of ridge cap, and 14 pieces of drip edge.
Frequently asked questions
A second look at the estimate.
How many bundles of shingles do I need?
Three bundles cover one square (100 square feet) for standard asphalt shingles. Multiply your squares by three and round up to whole bundles.
What is a roofing square?
One square is 100 square feet of roof surface, the trade unit asphalt shingles are sold in.
How does pitch affect the area?
A steeper pitch means more sloped surface than the horizontal footprint. The pitch factor converts footprint to the actual roof area.
Can I enter metric dimensions?
Yes. Metric mode uses metres for the footprint and ridge length. The pitch ratio stays the same.
How is the cost estimated?
Enter a price per bundle and the calculator multiplies it by the whole-bundle count. Without a price, no cost is shown.
Sources and limitations
This tool estimates shingle and accessory materials for a simple rectangular roof. It is a material estimate only — it does not provide engineering, structural, or safety conclusions, and it does not assess snow or wind load, deck condition, flashing, ventilation, or local building code requirements, or retrieve live prices.
- Asphalt Roofing Manufacturers Association — Residential Asphalt Roofing Manual — reference for shingle coverage and installation practice.
Bundle counts, underlayment coverage, ridge cap, and drip edge are planning estimates for a simple rectangular asphalt-shingle roof. This tool estimates materials only and does not provide engineering, structural, or safety conclusions. Confirm the exact product coverage and local code requirements before ordering.
Last reviewed: September 7, 2026