Roofing Sheet Calculator
Estimate the number of roofing sheets required for your project based on roof dimensions, sheet size, overlaps and waste allowance. The calculator also estimates roof area and fixing screw quantity.
Enter Your Roof Dimensions
Enter dimensions in metres. Use the slope length measured from the ridge to the eave, not the horizontal building width.
Estimated Material
Results update automatically when you change the dimensions.
Need an accurate quantity based on your roof drawing? Send the roof dimensions and required roofing profile to HESU.
Send Your Roof Drawing to HESUHow to Calculate the Number of Roofing Sheets
Roofing sheet quantity should be calculated from the installed coverage of each sheet, rather than simply dividing the roof area by the nominal sheet area. Corrugated and profiled roofing sheets normally overlap at the sides, and roofs requiring more than one row of sheets may also require an end overlap.
The calculator first determines the effective sheet width after the side overlap. It then calculates how many sheets are required along the roof length and how many rows are required from the eave to the ridge.
Roof Length
Roof length is measured parallel to the ridge or eave. This determines how many sheets are required across each horizontal row.
Roof Slope Length
Roof slope length is the actual distance measured along the roof surface from the ridge to the eave. Do not use only the horizontal building width when the roof is pitched.
Effective Roofing Sheet Width
Effective width is the usable installed coverage after the side lap between adjacent roofing sheets has been deducted. Different corrugated, trapezoidal, ASA, PVC and UPVC roofing profiles can have different nominal and effective widths.
Roofing Sheet Overlap
Side and end overlaps depend on the selected sheet profile, roof pitch, rainfall, wind exposure and installation specification. Always confirm the required overlap using the current product drawing or installation instructions before ordering material.
Allow for Cutting and Spare Sheets
A waste allowance is useful because real roofs can include hips, valleys, penetrations, edge cutting and damaged sheets. Simple rectangular roofs may require relatively little additional material, while complex roof layouts can require a larger allowance.
Roofing Sheet Calculator FAQ
How many roofing sheets do I need?
Enter the roof length, roof slope length, number of roof slopes, sheet dimensions and required overlaps. The calculator will determine the minimum number of sheets and add your selected waste allowance.
Should I calculate roofing sheets by square metres?
Roof area is useful for estimating project size, but sheet quantity should also account for the sheet profile and installed effective coverage. Nominal sheet area alone can underestimate material because adjacent sheets overlap.
What is effective width of a roofing sheet?
Effective width is the actual roof width covered by one installed sheet after the required side overlap has been considered. It is usually smaller than the total manufactured sheet width.
How much extra roofing material should I order?
The appropriate allowance depends on the roof design. A straightforward rectangular roof generally creates less cutting waste than a roof containing hips, valleys, penetrations or irregular dimensions. Confirm the final quantity from the project drawing before ordering.