Calculate roof area, roofing 'squares' (US construction unit, 100 sq ft) and shingle bundles needed. Adjusts for roof pitch - steep roofs have more surface area than the floor plan suggests.
e.g. 5 means 5/12
Roof area
1,300 sq ft
Pitch factor 1
With wastage
1,430 sq ft
Squares
14
100 sq ft each
Shingle bundles
44
3 / square
Часть содержимого пока показывается на английском.
Roofing material estimation is a high-stakes calculation - under-order and your project stalls mid-installation while you wait for fresh stock; over-order and you waste money plus disposal cost on leftover sheets and bundles. Indian roofing varies widely: most urban apartments and independent houses use RCC flat slabs with waterproofing chemicals and tile finish; rural and semi-urban homes often use sloped roofs with GI corrugated sheets, color-coated metal sheets (CGI), Mangalore tiles, or asbestos cement sheets. Hill stations and high-rainfall regions like Kerala, Mangalore, Goa, Northeast India, and the Western Ghats use steeper pitches (8/12 to 12/12) for monsoon drainage; plains regions use gentler slopes.
This calculator computes the true sloped roof area from your house footprint length, width, and roof pitch, then converts to standard construction units (US 'squares' of 100 sq ft) and shingle bundles for ordering. The key insight: a pitched roof has more surface area than its floor plan - a 5/12 pitch increases area by about 8%, an 8/12 pitch by about 20%, and a 12/12 (45 degree) pitch by 41%. Always include the pitch factor when ordering, otherwise you'll fall short. For Indian metal sheets sold in standard sizes (e.g., 8 ft, 10 ft, 12 ft lengths × 3 ft widths), convert the computed roof area to sheet count after applying 10-15% wastage.
Enter house length and width (footprint).
Enter roof pitch as rise per 12 inches of run (e.g. 5 means 5/12 pitch).
Adjust layers and waste % if needed.
Read roof area, squares and shingle bundles.
Plan area = L × W. Pitch factor = √(rise² + 12²) / 12 - multiplies plan area to actual sloped surface. Three bundles of asphalt shingles cover one square (100 sq ft).
Pitch factor = √(rise² + 144) / 12 Roof area = Plan area × Pitch factor Squares = Roof area / 100
Pitch factor (slope multiplier): √(rise² + 12²) / 12. For 5/12 pitch: √(25 + 144)/12 = √169/12 = 13/12 = 1.083. So roof area = plan area × 1.083. For 12/12 (45°): √(144+144)/12 = √288/12 = 1.414. The pitch factor is just the hypotenuse-over-run ratio for the triangular roof section. Always apply this multiplier; ignoring it is the #1 source of roof material shortages.
Roof area = (length + 2×overhang) × (width + 2×overhang) × pitch factor. Typical Indian eave overhang is 1-2 feet to protect walls from monsoon rain. Add this to your footprint before applying pitch factor for accurate material estimation. For complex roofs (gables, hips, valleys), break into rectangles, apply pitch factor to each, and sum.
Material conversion: one US 'square' = 100 sq ft. Three bundles of standard 3-tab asphalt shingles cover one square. For Indian metal sheets, sheet area = length × width (e.g., 8 ft × 3 ft = 24 sq ft per sheet). Need = roof area / (sheet area × (1 - overlap factor)). Overlap factor 10-15% accounts for sheet overlap between adjacent rows (typical 100 mm side lap, 150 mm end lap on GI sheets). Add 10% wastage for cuts at hips, valleys, edges and ridges.
Plan area = 1200 sq ft. Pitch factor = 1.083. Roof area = 1300 sq ft. Add 1 ft overhang each side: footprint 42×32, area 1344, with pitch 1456 sq ft. Effective sheet coverage 80% (overlaps): need 1456/(24×0.8) = 76 sheets. Add 10% wastage = 84 sheets to order.
Plan area = 750 sq ft. Pitch factor = √(64+144)/12 = 1.20. Roof area = 900 sq ft. With 2 ft overhang on all sides for monsoon protection: 34×29 = 986 sq ft plan, × 1.20 = 1183 sq ft sloped. Order accordingly.
Plan area 2000 sq ft. Pitch factor √(36+144)/12 = 1.118. Roof area = 2236 sq ft = 22.36 squares. Bundles needed = 22.36 × 3 = 67 bundles + 10% waste = 74 bundles.
Low-slope: 2/12 to 4/12. Standard residential: 4/12 to 8/12. Steep: 9/12 and above. Indian RCC flat roofs are usually 1/100 (drainage slope).
Cuts at hips, valleys and edges leave scraps. 10% wastage is typical, more for complex roofs with many faces.
Add eave overhang (typically 1-2 ft) to length and width before computing. Calculator currently uses just plan dimensions.
Metal sheets (GI / colour-coated) are sized in sq m or pieces. Same area math applies - use roof area and divide by sheet size.
Renovating, decorating or estimating utilities at home almost always reduces to three numbers - area, volume, and cost. Get any of them wrong by 10% and you're either short of paint and tile, or you've over-ordered and have to return material. This calculator uses the same wastage allowances, packing rules and unit conversions that contractors and material suppliers actually use in India.
Use it together with the paint, tile, electricity bill and BTU calculators to plan a complete renovation budget. Indian states have very different electricity tariffs and material prices, so the calculators expose state-wise tariffs (Maharashtra MSEDCL, Tamil Nadu TANGEDCO, Delhi BSES, Karnataka BESCOM, etc.) and let you override defaults to match your supplier's pricing.
The Roofing Calculator is part of the Home & Lifestyle suite on Online Calculator Tools, alongside 6 related calculators. All tools share the same UI patterns, the same privacy-first rendering (nothing is sent to a server), and the same commitment to showing the formula and assumptions behind every result.
