Roofing Calculator

Free

Roofing · Squares, bundles and accessories · default waste 10%

Enter your measurements

Numbers start at typical defaults — change anything. Every result states the inputs and assumptions used.

Roof length (per section)(ft)

Roof width (per section)(ft)

Identical roof sections

Pitch

Eaves / starter course(linear ft)

Ridge length(linear ft)

Hip length(linear ft)

Valley length(linear ft)

Penetrations (vents, stacks, flues)

Waste factor(%)

Applied once to each material quantity, then rounded up to the orderable increment.

Product assumptions — editable5

Sheet sizes, coverage rates, bundle counts, bag yield and similar come from the product you are buying. Change any of them to match your supplier — whatever you set is shown again with the result.

Bundles per square

3 bundles per square for most 3-tab and architectural shingles. Confirm on the bundle label.

Underlayment coverage per roll(sq ft)

A roll of synthetic underlayment typically covers about 10 squares (1,000 sq ft).

Ridge / hip cap coverage per bundle(linear ft)

Starter course coverage per bundle(linear ft)

Valley flashing stock length(ft)

Enter your measurements and press "Calculate materials" to see the calculated quantity, waste-adjusted quantity and recommended order quantity.

What this calculator does

•Slope multiplier = √(144 + pitch²) ÷ 12
•Roof area = length × width × sections × slope multiplier
•Squares = roof area ÷ 100
•Bundles = squares × bundles per square
•Underlayment rolls = roof area ÷ roll coverage; starter and ridge cap bundles = linear ft ÷ coverage per bundle

Deterministic by design: no AI, no lookups, no network calls — the same inputs always give the same numbers. Product values such as coverage rates and bundle counts are editable and shown with the result.