How many roof sheets do I need for a 20x30 shed?

For a 20x30 ft single slope shed using standard GC corrugated sheets (0.47mm thick, 12ft length), you need approximately 18 to 22 sheets depending on overlap and wastage allowance. Use the Roof Sheet Calculator above and enter your exact dimensions for a precise quantity.

What is the difference between effective cover and overall width?

Overall width is the full physical width of the sheet as manufactured — for a standard GC corrugated sheet this is 1000mm. Effective cover is the usable width after deducting the side lap overlap (typically 162mm for GC corrugated), giving an effective cover of 838mm per sheet. The calculator uses effective cover to compute how many sheets fit across your roof width.

Roof Sheet Calculator

Q: Which sheet thickness should I use for an industrial shed?

For industrial sheds and factories, 0.47mm or 0.50mm thick GI or colour coated sheets are the standard choice. The 0.47mm gauge is the most widely used for purlin spans up to 1.4m. For wider purlin spacings or high wind zones, 0.50mm or 0.55mm is recommended. Consult IS 277 and IS 875 for structural guidance.

Q: How much wastage should I add for a simple shed roof?

For a simple rectangular single-slope shed with no cuts or penetrations, add 5% wastage. For a moderate complexity roof with a few cuts or a ridge, use 8%. For complex roofs with multiple angles, skylights, or irregular shapes, use 10 to 12%. The calculator provides these three options in the wastage dropdown.

Q: Can I use this calculator for colour coated sheets?

Yes. The calculator supports both plain GI (galvanised iron) sheets and colour coated sheets. The sheet profiles — GC Corrugated, Trapezoidal, and Hi-Rib — are available in both GI and colour coated variants from brands like Tata Shaktee, JSW Colouron+, Jindal Panther, and APL Apollo. Select your brand and profile and the calculator will compute the correct quantities.

Calculate exact sheet quantity, weight, and accessories for any Indian shed or building. Supports GC corrugated, trapezoidal, and Hi-Rib profiles.

Enter Roof Details

Roof Length (metres) Measure along the roof slope

Roof Width (metres) Width perpendicular to ridge

Roof Type Single slope is most common for sheds

Sheet Profile GC Corrugated is standard for most sheds

Brand Choose Generic if brand doesn't matter

Sheet Thickness 0.47 mm is standard for residential and industrial

Sheet Length 12 ft (3660 mm) is the most common length

Wastage Allowance Simple = rectangular roof with no cuts

How to Use This Calculator

Enter roof dimensions — measure the length along the slope direction and the width perpendicular to the ridge. Use metres with one decimal place (e.g. 12.5 m).
Select your roof type — single slope is most common for industrial sheds. Gable roofs have two slopes; hip roofs have four.
Choose profile, brand, and thickness — GC Corrugated at 0.47 mm is the Indian standard for most sheds. Trapezoidal and Hi-Rib are used for longer spans and colour-coated applications.
Pick sheet length and wastage — 12 ft (3660 mm) sheets cover most spans efficiently. Add 5% wastage for simple rectangular roofs; use 8–12% if there are openings or complex cuts.
Click Calculate — you will instantly see sheet count, estimated weight, ridge caps needed, and fastener quantity. Use the Print button to save your Bill of Quantities.

Sheet Profile Specifications

All three profiles supported by this calculator, with key dimensions as per IS 277 and manufacturer standards.

Profile	Overall Width	Effective Cover	Side Lap	Rib Height	Min. Slope
GC Corrugated (Standard)	1000 mm	838 mm	162 mm	17 mm	5°
Trapezoidal Profile	1000 mm	900 mm	100 mm	35 mm	3°
Hi-Rib Profile	762 mm	686 mm	76 mm	51 mm	2°

Frequently Asked Questions

How many roof sheets do I need for a 20×30 shed?

For a 20×30 ft (approximately 6×9 m) single-slope shed using standard GC corrugated sheets at 0.47 mm thickness and 12 ft (3660 mm) length, you will typically need 18 to 22 sheets. The exact count depends on the effective cover width of your chosen profile, the end lap, and your wastage allowance. Enter your dimensions above for a precise figure.

What is the difference between effective cover width and overall width?

The overall width is the full width of the sheet as supplied — 1000 mm for standard GC corrugated. The effective cover width is the area actually covered after accounting for the side lap where adjacent sheets overlap. For GC corrugated, the effective cover is 838 mm because each sheet overlaps the next by 162 mm (one and a half corrugations). Always use the effective cover width when calculating how many sheets span across the roof width.

Which sheet thickness should I use for an industrial shed?

For standard industrial and warehouse sheds in India, 0.47 mm thick GC corrugated or trapezoidal sheets are the most common choice. They meet IS 277 requirements for general industrial use and offer a good balance of strength and cost. For coastal areas, heavy rainfall zones, or spans above 1.5 m between purlins, 0.50 mm or 0.55 mm is recommended. Use 0.63 mm only for cyclone-prone regions or very long purlin spans.

How much wastage should I add for a simple shed roof?

For a simple rectangular single-slope shed with no skylights, ventilators, or ridge openings, a 5% wastage allowance is sufficient. This covers minor cutting at the gable ends and any damaged sheets. Use 8% if your roof has openings such as ridge ventilators, pipe penetrations, or a small number of hip cuts. For complex roofs with valleys, multiple hips, or many penetrations, add 12% wastage to avoid running short.

Can I use this calculator for colour coated sheets?

Yes. Colour coated sheets from brands like JSW Colouron+ and Tata Shaktee are available in all three profiles — GC corrugated, trapezoidal, and Hi-Rib — and follow the same effective cover dimensions as plain GI sheets. Select your brand from the Brand dropdown and the appropriate profile. The sheet count calculation is identical; only the weight estimate varies slightly because colour-coated sheets have a slightly higher base metal weight due to the paint system.