Flat Roof Calculator
Estimate flat roof area, material quantities, and optional material cost using your roof dimensions and product coverage.
Roof details
All sections are assumed to have the same length and width.
Extra material allowance; actual waste depends on the roof layout and product instructions.
Material estimate
Material selection is descriptive only; it does not set a market price or product coverage.
Default is an editable example. Use the effective coverage stated by your supplier.
Optional. Enter your supplier's price; no market price is assumed.
YOUR ESTIMATE
Total roof area
1,200 sq ft
Across 1 roof section
Area with waste
1,320 sq ft
Roofing squares
13.2
Coverage per roll/package
215 sq ft
Rolls/packages needed
7
Estimated material cost
$0.00
Roof plan preview
Illustrative top view only; the diagram is not a construction drawing.
How to Use the Calculator
- Choose feet/inches or meters/millimeters.
- Enter the length and width of one roof section, then enter the number of equally sized sections.
- Set a waste factor to allow for cuts and material handling.
- Select a material label and enter the coverage shown by your supplier for one roll or package.
- Optionally enter the price per roll/package to estimate material cost.
How It Works
The calculator multiplies roof length by width and the number of sections. It then applies the waste factor, divides the adjusted area by the entered product coverage, and rounds the quantity up to a whole roll or package. Roofing squares are shown in imperial units only.
Assumptions and Limitations
- All roof sections are assumed to be rectangular and have the same dimensions.
- Area is based on the entered plan dimensions. Roof slope, parapets, upstands, flashing, penetrations, and other details are not measured separately.
- The waste factor is a planning allowance, not a guarantee of actual material usage.
- Product coverage and price must be checked against the supplier's specifications. Material type does not automatically determine coverage or cost.
- The cost estimate covers material rolls/packages only. Labor, accessories, insulation, tear-off, disposal, delivery, taxes, and other project costs are excluded.
