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Roof Tile Calculator

Plan area divided by cos(pitch) is the sloped area; count tiles after laps and waste.

Quick answer

With the default inputs: Plan area 100 m² · Roof pitch 30° · Tile width 0.33 m etc.Tiles incl. waste 1190 blocks

Use your own dimensions ↓

Inputs

m²
°
%

Result

Tiles incl. waste
1190blocks
Roof factor1.1547
Sloped area115.5m²
Effective cover per tile0.1020m²
Tiles net1133blocks
Batten length340m
Tiles per m²9.8blocks/m²
How this is worked out

Sloped roof area is not plan area. Sloped area = plan area / cos(pitch): at 30 degrees the factor is about 1.155, so 100 m² of plan becomes 115.5 m² of roof, and at 45 degrees the factor is 1.414, a 41% increase. Quoting materials off plan area alone is the commonest mistake and under-orders by 10-40%. Tiles are counted by effective cover, which is (tile width - side lap) x (tile length - head lap), because every tile overlaps the one below. A typical 330x420 concrete tile with 30 mm side lap and 80 mm head lap covers about 0.102 m², roughly 9.8 tiles per m². Waste is normally 5%, rising to 8-10% for complex roofs with valleys and dormers. Batten length is sloped area divided by spacing, plus extra rows at the ridge, eaves and valleys.

Next up: Roof Flashing Calculator · Roof Sheathing Calculator

Formula

Roof factork = 1 / cos(pitch)
Sloped areaAs = Aplan × k
Effective covera = (w − side lap) × (l − head lap)
Tiles netn = ⌈As / a⌉
With wasteN = ⌈n × (1 + waste)⌉
Batten lengthL = As / batten spacing
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 typeSize (mm)Side lap (mm)Headlap (mm)Effective cover (m²)Per m²Sold by
Cement plain tile330×42030800.10209.8pcs
Cement profiled tile300×40025750.089411.2pcs
Clay pantile300×40030700.089111.2pcs
Clay plain tile200×30020600.043223.1pcs
Glazed barrel tile150×3000600.036027.8pcs
Slate, 100 mm headlap400×25001500.040025.0pcs
Asphalt 3-tab shingle337×100008570.048220.8bundle
Metal sheet roofing1300×42001000.41602.4sheet

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)

GradeBundles per squareCover per bundle (m²)1 square (m²)100 m² roof200 m²300 m²
3-tab33.109.2903336597
Architectural / dimensional33.109.2903336597
Premium / luxury42.329.29034487130
Heavyweight51.869.290354108162

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.

Basis

FAQ

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.

Cite this page

Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Roof Tile Calculator. 2026-10-25. https://jianzhujisuan.com/en/roof-tile-quantity

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.