Roofing Shingle Calculator
Estimate shingles for a straightforward gable roof. Enter the roof area — or the footprint and pitch — and get squares, field bundles, and optional ridge cap and starter, with a waste margin for cuts and starter courses.
Measured along the slope, all planes added together.
Covers a simple gable roof. Include the overhang in the footprint if you have it.
Most architectural shingles are 3 bundles per square — confirm on the wrapper.
Advanced: ridge cap, starter & price
Coverage per bundle varies by product — read it off the ridge cap and starter wrappers.
Formula & how it works
From footprint: roof area = length × width × √(1 + (pitch ÷ 12)²). Squares = roof area ÷ 100.
Field bundles = squares × (1 + waste) × bundles per square, rounded up. Ridge cap and starter are their linear length ÷ the coverage per bundle, rounded up.
Worked example
A 40 × 30 ft footprint at a 6-in-12 pitch has a slope factor of about 1.12, so the roof surface is roughly 1,342 ft² — about 13.4 squares. At 3 bundles a square with 10% waste, that's 45 field bundles. Add 40 ft of ridge (2 bundles) and 80 ft of eaves (1 starter bundle) for 48 total.
Ordering shingles
Measure on the slope, not the ground
The single most common mistake is using the house footprint as the roof area. A roof climbs, so its real surface is bigger — and steeper roofs are bigger still. If you know the pitch, this tool applies the slope factor for you; if you've measured the roof planes directly, enter that area instead and skip the pitch math.
Bundles per square comes off the wrapper
Three bundles cover a square for most architectural shingles, but some heavier or designer lines run four, and three-tab can differ too. Check the wrapper and enter the real number, since being off by one bundle per square adds up quickly over a whole roof.
Don't forget the edges
Ridge cap runs along every ridge and hip, and starter strip runs along the eaves and often the rakes. Both come in their own coverage per bundle, printed on the package. Leaving them out is an easy way to come up short on the last day of the job.