New Zealand · metal roofing
Roof sheet calculator
Sheet count is cover width across the ridge, rounded up, once per plane. It is not sloped area divided by a made-up sheet size.
For a gable, take the ridge-direction width (building length plus verges) and divide by the profile’s effective cover. Round each plane up, then multiply by two. A 12.1 m ridge on 762 mm corrugate is 16 sheets per plane, 32 total — not 15.9 × 2 with a prayer.
Hip roofs cannot be counted that cleanly because every sheet on the ends is a diagonal cut. This calculator switches to area ÷ (cover × common-rafter length) and applies a higher waste percentage. That is an order estimate, not a cutting list.
Always type the cover from the coil tag if it differs from the library. A 5 mm cover error on a long building is a missing sheet.
FAQ
Should both gable planes use the same length?
Yes on a symmetric gable with equal eaves. If one eave is a boxed return or a different overhang, split it into two sections.
What about end laps?
True longrun is usually one sheet ridge-to-eave. End laps only appear if you hit a length cap (truck, site, expansion). Set a sheet length cap on the takeoff to force that conversation.