Roofing Sheet and Roof Tile Calculator

How many sheets does a roof need?

Trapezoidal sheets, sandwich panels and corrugated sheets are laid with side laps. So the calculation uses the cover width of the sheet, not its overall width. The number of sheets in a row is the eaves length divided by the cover width, rounded up: sheets = ⌈eaves length / cover width⌉.

Are end laps needed up the slope?

If the slope length is shorter than one sheet, a single sheet per row is enough. If it is longer, sheets are joined end to end and each joint loses the lap length. n sheets cover n × sheet length − (n − 1) × lap. The calculator finds the smallest n that works.

Roof tiles

For tiles the manufacturer gives the number per square metre. The calculation is tiles = area × tiles per square metre × (1 + waste). For common clay tiles that figure is roughly 10 to 16 and depends on the batten gauge.

Example

A gable roof with two faces, each 11 m along the eaves and 5.2 m up the slope, covered with sheets of 1000 mm cover width and 6 m length needs 11 sheets per face, 22 in total. If the slope length were 10 m, a 20 cm end lap would mean 2 sheets per row.

Limits

The calculation is for rectangular faces. If you do not know the roof area or slope length, use the roof area and pitch calculator first. Ridge caps, valleys and fasteners are counted separately.