Sheet count for tray is still ceil(width ÷ effective cover). The trap is using this site’s 300 mm placeholder, or the overall coil width, instead of the named pan. General formula: cover-width sheet count. Which tray to pick: secret-fix tray.
What to write down
From the current product sheet: manufacturer, pan name, effective / net cover in mm, overall width (do not use this for count), clip or seam type. Enter that cover in the override box on NZ Roof Tools. Leave 300 mm only if you have not named a product yet; then treat the sheet count as provisional.
Typical NZ pans sit around 265–500 mm. Heritage Tray (Dimond example) is about 450 mm cover / 465 mm overall / 3°. A 9.000 m plane: 9.000 ÷ 0.300 = 30 sheets; ÷ 0.450 = 20; ÷ 0.465 overall = 19.35 → 20 still, but 325 mm overall on the placeholder (9.000 ÷ 0.325) is 28 and a shortage if the real pan is 300 mm.
After the millimetres
Pitch, run, flashings, and hips are not in the cover number. Tray flashings are grab / verge / ridge / wall, not corrugate barge. Extra High still changes junction cover. Hips need waste on top of the cover count.
If the pan is unnamed, the cladding pitch is below that sheet’s minimum, or the run exceeds the PTS, stop the order. NZMRM CoP and the named sheet remain the authority.