Kumar IronRoofing sheet calculator
Work out how many roofing sheets, ridge caps and fasteners a shed or roof needs before you order.
Formula
Slope length = run ÷ cos(pitch). Sheets down = (slope length − end overlap) ÷ (sheet length − end overlap), rounded up. Sheets across = roof length ÷ effective cover width, rounded up. Ridge caps = roof length ÷ (2 m − 150 mm). Fasteners = sheets × purlin crossings × 3, plus 5%. Enter dimensions including any overhang.
Overall width 1060 mm minus side overlap gives an effective cover of 1000 mm. Widths are typical; confirm with the sheet you buy.
- Roof area: 63.9 m² (687 sq ft), slope length 3.19 m
- Sheets: 40 of 10 ft (10 across × 2 down × 2 slopes)
- Ridge caps: 6 (2 m pieces, 150 mm overlap)
- J-hooks or screws (with washers): 378
- Least waste for this roof: 11 ft sheets
Estimate only. Sheet widths, overlaps and fastener spacing vary by profile and maker, so confirm with your roofer before ordering.
Need roofing sheets?
We stock roofing sheets and fabrication material. See our roofing sheets or check the roofing sheet weight chart.
FAQ
- How many roofing sheets do I need for a shed?
- Divide the roof length by the sheet's effective cover width and round up for sheets across. Divide the slope length by the sheet length less end overlap and round up for sheets down. Multiply the two, and by 2 for a gable roof.
- What is effective cover width?
- The width a sheet covers once the side overlap is taken out. A trapezoidal sheet of about 1060 mm overall with a 60 mm overlap covers roughly 1000 mm. Check the exact figure for your sheet.
- How do I find the slope length?
- Slope length = horizontal run ÷ cos(pitch angle). For a gable roof the run is half the width. A 6 m wide gable at 20 degrees has a slope length of about 3.19 m per side.
- How many screws or J-hooks per sheet?
- This calculator assumes 3 per purlin crossing, purlins every 1.2 m, plus 5% extra. Your roofer's spacing may differ, so treat it as a starting count.
- Does this include wastage?
- Sheets are rounded up per row and column but no extra cut allowance is added. Add a few spare sheets for cutting and damage.
Send us your roof size and sheet length and we will quote the full order.