# Roof Tile Calculator Plan area divided by cos(pitch) is the sloped area; count tiles after laps and waste. - Page: https://jianzhujisuan.com/en/roof-tile-quantity - Category: Construction (https://jianzhujisuan.com/en/c/construction) - Chinese version: https://jianzhujisuan.com/zh/roof-tile-quantity.md - Data checked: 2026-10-25 ## Quick result With the default inputs (Plan area 100 m², Roof pitch 30 °, Tile width 0.33 m, Tile length 0.42 m, Side lap 0.03 m, Head lap 0.08 m, Waste 5%, Batten spacing 0.34 m): **Tiles incl. waste 1190 blocks** ## Inputs | Parameter | Type | Default | Unit | Note | |---|---|---|---|---| | Plan area | number | 100 | m² | | | Roof pitch | number | 30 | ° | | | Tile width | number | 0.33 | m | | | Tile length | number | 0.42 | m | | | Side lap | number | 0.03 | m | | | Head lap | number | 0.08 | m | | | Waste | number | 5 | % | | | Batten spacing | number | 0.34 | m | | ## Formula - **Roof factor**: k = 1 / cos(pitch) - **Sloped area**: As = Aplan × k - **Effective cover**: a = (w − side lap) × (l − head lap) - **Tiles net**: n = ⌈As / a⌉ - **With waste**: N = ⌈n × (1 + waste)⌉ - **Batten length**: L = As / batten spacing ## Worked example 100 m² plan, 30° pitch, 330×420 mm tiles, 30 mm side lap, 80 mm head lap, 5% waste: factor 1.1547, 115.5 m² sloped, 0.102 m² per tile, 1133 tiles net, 1190 with waste, about 9.8 tiles per m². ### Effective cover and quantity per m² by tile type (cover = (width − side lap) × (length − headlap), the same rule this page uses) | Tile type | Size (mm) | Side lap (mm) | Headlap (mm) | Effective cover (m²) | Per m² | Sold by | |---|---|---|---|---|---|---| | Cement plain tile | 330×420 | 30 | 80 | 0.1020 | 9.8 | pcs | | Cement profiled tile | 300×400 | 25 | 75 | 0.0894 | 11.2 | pcs | | Clay pantile | 300×400 | 30 | 70 | 0.0891 | 11.2 | pcs | | Clay plain tile | 200×300 | 20 | 60 | 0.0432 | 23.1 | pcs | | Glazed barrel tile | 150×300 | 0 | 60 | 0.0360 | 27.8 | pcs | | Slate, 100 mm headlap | 400×250 | 0 | 150 | 0.0400 | 25.0 | pcs | | Asphalt 3-tab shingle | 337×1000 | 0 | 857 | 0.0482 | 20.8 | bundle | | Metal sheet roofing | 1300×420 | 0 | 100 | 0.4160 | 2.4 | sheet | The headlap column is tile length minus exposure, which is why the slate and asphalt figures look large: a 250 mm slate with a 100 mm exposure has a 150 mm headlap, and a 1000 mm shingle with a 143 mm (5½ in) exposure has 857 mm. The same figure is what goes into this page, because it works on length minus headlap. Barrel tiles have no side lap (they interlock), and neither do shingles or metal sheets, hence the zero. Do not skip the last column: cement, clay and glazed tiles are ordered by the piece, asphalt by the bundle, metal sheet by the sheet or the metre — mix those three up and the bill of materials will not reconcile. None of the per-m² figures include waste; add 3-5% on site, and allow separately for hips, ridges and verges. ### Ordering asphalt shingles the US way: square and bundle conversions (net quantities, no waste added) | Grade | Bundles per square | Cover per bundle (m²) | 1 square (m²) | 100 m² roof | 200 m² | 300 m² | |---|---|---|---|---|---|---| | 3-tab | 3 | 3.10 | 9.2903 | 33 | 65 | 97 | | Architectural / dimensional | 3 | 3.10 | 9.2903 | 33 | 65 | 97 | | Premium / luxury | 4 | 2.32 | 9.2903 | 44 | 87 | 130 | | Heavyweight | 5 | 1.86 | 9.2903 | 54 | 108 | 162 | One square is 100 ft² or 9.2903 m² — not 1 m² and not 100 m², and the three sit an order of magnitude apart, which is where this convention goes wrong. Bundles per square sets the cover: at 3 bundles to the square each covers 3.10 m², at 5 bundles only 1.86 m², so one bundle can differ by 67% depending on grade. The three roof-area columns are net sloped area, with no waste and excluding ridge and starter courses; add 5-10% to suit site practice. Hip, valley and verge units are separate line items and are not covered here. ## Questions ### Why can't I use plan area to order tiles? Because tiles lie on the slope and the slope is bigger than its plan projection. The steeper the roof the bigger the gap: 3.5% more at 15 degrees, 15.5% at 30, 41.4% at 45 and 100% at 60. Ordering off plan area under-orders by 13% at 30 degrees and 29% at 45, and the job stalls waiting for material. Convert to sloped area first, then multiply by tiles per m². ### What waste allowance should I use? 5% normally. Increase it where there is a lot of cutting: valleys, dormers and parapet returns take 8-10%; profiled tiles or tiles that need site drilling take 10%; cut verges take 8%. Keep 3-5 spare tiles as well for later repairs - tiles are slightly colour-batched, and a patch added a year later will be visibly different. ### How is batten spacing set? It equals the exposed length of the tile after the headlap — tile length minus headlap. A 420 mm cement plain tile with an 80 mm headlap exposes 340 mm, so battens go at 340 mm centres; a 300 mm clay plain tile with 60 mm headlap gives 240 mm. Get one course wrong and the error accumulates up the slope until the ridge will not close, so set out from the ridge downwards and check against the eaves. ### How many square metres are in a bundle of asphalt shingles? Shingles are sold by the bundle, and 1 square is 100 ft² or 9.29 m². Both 3-tab and architectural grades run 3 bundles to the square, so one bundle covers 3.10 m²; premium at 4 bundles to the square covers 2.32 m² and heavyweight at 5 covers 1.86 m². Do not convert through a piece count — cover per bundle depends on the grade and varies between makers, so check the figure printed on the wrapper before ordering. ### Should roof area be measured on plan or on the slope? Order tiles on the sloped area. Sloped area = plan area ÷ cos(pitch): 1.155 at 30°, 1.221 at 35° and 1.414 at 45°. A 100 m² plan on a 45° roof is really 141.4 m², so ordering off the plan leaves you 30% short. Scaffolding, safety netting and membrane are quoted on different conventions by different trades, so agree which area is being measured before signing. ### Do slate and barrel tiles need battens? No. Slate is nailed straight to sarking boards, barrel tiles are bedded in mortar, metal sheet fixes to purlins and asphalt shingles nail to the deck. The batten quantity for all of these is zero, so carrying this page's batten line across to them produces a length that should not exist. ## Related tools - [Plaster and Render Calculator](https://jianzhujisuan.com/en/plaster-coat): Mortar, cement and sand by layer for internal plastering. - [Mortar Mix Design Calculator](https://jianzhujisuan.com/en/mortar-strength): Trial strength, cement, water and sand, and the mix by mass. - [Labour Days and Crew Calculator](https://jianzhujisuan.com/en/labor-productivity): Man-days, crew size and labour cost from output rates. - [Line-of-Balance Duration Calculator](https://jianzhujisuan.com/en/schedule-flow): Rhythmic flow duration with overlap and break adjustments. - [Material Storage Area Calculator](https://jianzhujisuan.com/en/material-storage): Net footprint, total area and a suggested bay size. - [Dewatering Calculator](https://jianzhujisuan.com/en/dewatering): Pit inflow by the equivalent-well method, then well count. --- Generated by BuildCalc. All calculations run in your browser; no data is uploaded. Formulas follow national standards and common trade practice; local codes govern.