For a simple gable, count sheets from cover width across the ridge, once per plane, round up, then ×2 if both sides match. Arithmetic: sheet count from cover. Tool: roof sheet calculator.
Example: 8.4 m plane, 762 mm cover → 11.02 → 12 sheets that side. Not sloped area divided by 0.85 m.
Then the rest of the order
- Length: slope including eaves; merchant cut (here rounded 50 mm). Check CoP run after 15/20/40/60 m depending on profile.
- Pitch: 8° corrugate, 4° Six Rib, 3° Hi Five/T-Rib/generic tray. Design pitch ≠ cladding pitch.
- Hips/valleys: extra waste, not the gable formula (waste).
- Flashings: separate lm (flashing checklist).
- Several pitches: several sections (multi-section).
Do not order from a US “square” or a 10% fudge on plan m². Put the named profile on NZ Roof Tools, screenshot the sheet count and warnings, and check the current NZMRM CoP before the yard cuts coil.