Free calculator
Roofing Material Calculator
Calculate purchase units for underlayment, drip edge, ridge cap, fasteners, and other roofing accessories -- from your own measurement and your product's own coverage figures.
Calculate your material quantity
Enter your measurement and coverage above, then select "Calculate purchase units" to see your results.
Coverage & accuracy
What this calculator is -- and is not
- This calculator computes one material at a time -- it is not a complete multi-material roof takeoff.
- There is no built-in coverage default for any product. You supply your own measurement and your product's own coverage figure from its packaging or spec sheet.
- Enter your own already-final measurement, including any waste allowance you want to add -- this calculator does not add one automatically.
- Purchase units are always rounded up to the next whole unit, since you cannot buy a fraction of a roll, bundle, or box.
- Always verify the manufacturer's coverage specification before purchasing -- coverage varies by product.
The three coverage methods
Area, linear, and roofing-square coverage explained
Area coverage
Used for materials like underlayment, ice-and-water membrane, and sheet goods: enter the area you need to cover (in square feet) and the area one purchase unit covers (also in square feet).
Linear coverage
Used for materials like drip edge, ridge cap, starter strip, and flashing: enter the length you need to cover (in linear feet) and the length one purchase unit covers (also in linear feet).
Roofing-square coverage
Used for materials specified per roofing square, such as some fasteners: enter the number of roofing squares you need to cover and the number of roofing squares one purchase unit covers (1 roofing square = 100 ft²). Need to convert a raw area into roofing squares first? Use the Roofing Square Calculator.
Worked examples
Worked examples for each coverage method
Area coverage: 3,438.4 ft² of underlayment needed, at 1,000 ft² of coverage per roll, is exactly 3.4384 rolls -- rounded up to 4 rolls to purchase.
Linear coverage: 240 ft of starter strip needed, at 100 ft of coverage per bundle, is exactly 2.4 bundles -- rounded up to 3 bundles to purchase.
Roofing-square coverage: 34.384 roofing squares of fasteners needed, at 20 roofing squares of coverage per box, is exactly 1.7192 boxes -- rounded up to 2 boxes to purchase.
Before you buy
Always verify the manufacturer's specification
Coverage per roll, bundle, or box varies by manufacturer and by product line. This calculator never assumes or defaults a coverage figure for any material -- always check the product packaging or the manufacturer's specification sheet for the exact coverage of what you plan to buy before purchasing.
FAQ
Frequently asked questions
How do I calculate how much roofing underlayment I need?
Underlayment is area coverage: divide the total area you need to cover (in square feet) by the coverage one roll provides (also in square feet), then round up to the next whole roll -- you cannot buy a fraction of a roll. Select "Area coverage" and enter your own roof area and your product's coverage per roll from its packaging.
How do I calculate drip edge or ridge cap length?
Drip edge, ridge cap, starter strip, and similar trim pieces are linear coverage: divide your required linear feet by the linear feet one piece or bundle covers. Select "Linear coverage" and enter your own measured length and your product's coverage per unit.
What does roofing-square coverage mean?
Some products -- fasteners and certain accessories -- are specified by how many roofing squares one box or unit covers (1 roofing square = 100 ft²). Select "Roofing-square coverage" and enter the number of roofing squares you need to cover and how many squares one purchase unit covers, both from the product packaging.
Is this the same as the Roofing Shingle Calculator?
No. This calculator handles generic roofing accessories and materials (underlayment, drip edge, ridge cap, fasteners, and similar). Shingle bundle conventions -- and the specific rounding and terminology suppliers use for shingles -- are handled more clearly by the dedicated Roofing Shingle Calculator.
Does this calculator know my product's coverage rate?
No. Coverage varies by manufacturer and product, so this calculator never assumes or defaults a coverage figure -- always check the packaging or the manufacturer's specification sheet for your specific product before entering a number here.
Does this calculator save or store my numbers?
No. Everything runs in your browser and nothing you enter here is saved, sent to a server, or stored in any way -- reloading the page clears the form.
Next step
Already have your measurements? Turn them into a profitable estimate.
Roofing Estimate Pro helps contractors apply true material and labor costs, include overhead, price for a target margin, save estimates on this device, and produce a customer-ready proposal -- all from measurements you already have.
Build a profitable estimate