Formula
Sheets per row (one side) = roof width ÷ 2.33 ft (round up) Total sheets = per-row × slopes (1/2) + wastage % Bundles = total sheets ÷ pieces per bundle (round up)
- A sheet is nominally 32 inches wide but covers ≈ 28 inches = 2.33 ft after side overlap.
- 1 ban = 72 ft (70 ft for 7/10 ft sheets). Pieces per bundle = 72 (or 70) ÷ sheet length.
- There is no fixed wastage rate — the calculator defaults to 10%, change it freely.
Example
A 30×20 ft double-slope roof, 8 ft sheets, 10% extra:
Sheets per row per side = 20 ÷ 2.33 = 8.57 → 9. Double slope: 9 × 2 = 18, with 10% extra ceil(19.8) = 20 sheets. At 72 ÷ 8 = 9 pieces a bundle, bundles = 20 ÷ 9 = 2.22 → 3 bundles.
At the default Tk 8,300/bundle (PHP plain 0.42 mm), tin cost = 3 × Tk 8,300 = Tk 24,900.
With accessories: screws ≈ 125 × 3 = 375 pcs (count only), ridge ≈ Tk 55 × 30 ft = Tk 1,650, labour ≈ Tk 1,250 × 3 = Tk 3,750. Grand total = 24,900 + 1,650 + 3,750 = Tk 30,300.
Bundle and price table
| Sheet length | Pieces per bundle | Bundle feet |
|---|---|---|
| 12 ft | 6 | 72 ft |
| 9 ft | 8 | 72 ft |
| 8 ft | 9 | 72 ft |
| 6 ft | 12 | 72 ft |
| 10 ft | 7 | 70 ft |
| 7 ft | 10 | 70 ft |
Default per-bundle prices (single dealer — replace with yours): PHP plain 0.42 mm Tk 8,300 · PHP plain 0.32 mm Tk 6,290 · PHP plain 0.22 mm Tk 5,020 · PHP colour 0.42 mm Tk 9,200 · AKS plain 0.42 mm Tk 8,100 · AKS plain 0.32 mm Tk 6,050 · AKS plain 0.19 mm Tk 4,250 · AKS colour 0.42 mm Tk 9,250.
What to know in Bangladesh
- Effective width is what counts: shops say 32 inches, but overlap leaves ≈ 28–30 inches. Measure the roof width and divide by that.
- Know brands by their mark: Abul Khair (cow), PHP Arabian Horse (horse); Jalalabad sells by SBW/weight, not mm.
- Never trust one shop’s price: defaults are one dealer’s (September 2026). Prices move with area, thickness and season — ask 2–3 shops.
- End-lap is separate: no reliable figure exists for overlap along the slope — agree it with your mason and fold it into the wastage %.
- Rough cross-checks: a 10×12-haath house ≈ 3–4 bundles, 15×20 ft ≈ 7–8, 20×30 ft ≈ 12–14 (dealers’ rules of thumb — slopes vary).
More: slope, overlap and wastage
Sheets run down the roof slope — the long side covers the slope, the wide sides join edge to edge. So the sheet count comes from the roof width, not its length. The length feeds the ridge-cap and labour estimates instead.
Side overlap eats one corrugation, so a 32-inch sheet covers ≈ 28 inches. Front-back overhang and end-lap along the slope differ per house — no reliable standard was found, so instead of a fixed constant the calculator lets you fold all of it into the wastage %. Use up to 15% for cut-up or crooked roofs; 5–10% is enough for a straight new roof.
No reliable mm–gauge–SBW conversion table was found, so this page ships none. Ask the shop for both mm and SBW and compare.