How Many Roof Tiles Per Square Metre? UK Guide
Published 2026-07-17 · Browse all tools
Ask how many roof tiles you need per square metre and you'll get one of two answers. Someone will say 60, someone else will say about 10, and both of them are right. Plain tiles and interlocking concrete tiles differ by roughly a factor of six, and the figure moves again with your headlap and your pitch.
So the honest answer is that tiles per m² isn't a property of "roof tiles". It's a property of your tile, at your lap, on your roof. The good news is the maths is short, and once you've seen it you can work out any tile from its datasheet in about fifteen seconds.
The two numbers that decide everything
Tiles per m² comes from exactly two measurements: gauge and cover width.
Gauge is the vertical spacing between batten centres. It sets how much of each tile is exposed to the weather once the course above laps over it.
Cover width is the horizontal equivalent, meaning the width of tile you actually see once it's interlocked or side-lapped with its neighbour. It's always less than the tile's nominal width. A 330mm tile might only give you 300mm of cover.
Multiply how many courses fit in a metre by how many tiles fit across a metre, and you have your figure:
Tiles per m² = (1000 ÷ gauge) × (1000 ÷ cover width)
Both in millimetres. That's the whole calculation.
The takeaway: if a supplier quotes you a tiles per m² figure without telling you the gauge it assumes, the figure is close to meaningless. Ask what lap it's based on.
Where gauge comes from
Gauge isn't given on the datasheet as a single fixed number, because it depends on the headlap you choose. But getting from headlap to gauge takes one line, and which line depends on whether your tile is single-lap or double-lap.
Single-lap tiles overlap only the course directly below. Interlocking concrete tiles and pantiles work this way.
Gauge = tile length − headlap
Double-lap tiles overlap the two courses below, so every part of the roof has two tiles over it. Plain tiles and slates work this way.
Gauge = (tile length − headlap) ÷ 2
That division by two is the entire reason plain tiles come in at 60 per m² while interlocking tiles come in at under 10. It isn't only that plain tiles are smaller. It's that you're effectively tiling the roof twice.
The takeaway: check the lap type before you calculate. Using the single-lap formula on a plain tile will underestimate your order by more than half.
Typical UK figures
Here's where the common tile types land at their standard headlap. These are the numbers to sanity-check yourself against.
| Tile type | Size (mm) | Cover width (mm) | Lap type | Headlap (mm) | Gauge (mm) | Tiles per m² |
|---|---|---|---|---|---|---|
| Plain tile | 265 × 165 | 165 | Double | 65 | 100 | 60.6 |
| Interlocking concrete | 420 × 330 | 300 | Single | 75 | 345 | 9.7 |
| Double Roman | 418 × 330 | 300 | Single | 63 | 355 | 9.4 |
| Natural slate | 500 × 250 | 250 | Double | 90 | 205 | 19.5 |
| Natural slate | 400 × 250 | 250 | Double | 90 | 155 | 25.8 |
| Fibre cement slate | 600 × 300 | 300 | Double | 100 | 250 | 13.3 |
Marley, Redland, Sandtoft, Russell Roof Tiles and Wienerberger all publish product-specific cover widths and maximum gauges, and they don't all agree even on nominally similar tiles. Treat the table as a reference point and the datasheet as the authority.
The takeaway: any figure you calculate that lands wildly outside these ranges means you've mixed up a lap type or a cover width.
The "60 tiles per m²" problem
Search for plain tile quantities and you'll be told 60 per m², over and over, as though it were a property of the tile. It isn't. It's a property of a 100mm gauge, which comes from a 265mm tile at a 65mm headlap. Change the lap and the number moves.
Drop your pitch below 35° and 65mm of lap stops being enough. Wind-driven rain travels further up a shallow roof, so the lap has to grow, often to 75mm or more. Take that same plain tile to a 90mm gauge and you get:
(1000 ÷ 90) × (1000 ÷ 165) = 67.3 tiles per m²
That's an 11% jump from the number everyone quotes. On a 70m² roof it's the difference between 4,276 tiles and 4,749 tiles. Nearly 500 tiles, or roughly £260 at typical 2026 merchant pricing, sitting in a gap that opened up because someone used a rule of thumb instead of their own lap.
The rule of thumb isn't wrong. It's just answering a question about a specific roof that might not be yours.
The takeaway: never take a tiles per m² figure without knowing what gauge it assumes. If you don't know the gauge, you don't have a figure, you have a guess.
Headlap isn't your choice alone
BS 5534:2014+A2:2018, the British Standard code of practice for slating and tiling, ties minimum headlap to roof pitch and site exposure. A sheltered plot in south Manchester and an exposed one on the Pennine edge above Rochdale will not get the same minimum lap out of the same tile, even at the same pitch.
The direction of travel is always the same. Shallower pitch means more lap. More exposure means more lap. More lap means tighter gauge, and tighter gauge means more tiles.
The same standard's 2014 revision also reset fixing expectations. Relying on nibs and the weight of the tile is no longer acceptable across large parts of a roof, and mechanical fixing is now the default in many situations rather than something reserved for perimeters. That doesn't touch your tiles per m², but it changes your clips, nails and labour, so it belongs in the same conversation as the tile order.
The takeaway: settle your headlap against the datasheet, your pitch and your exposure before any quantity maths happens. Everything downstream depends on it.
Worked example: a 1930s semi in Stockport
Numbers, on a real shape of roof.
Plain gable roof, 8.4m along the eaves, 4.2m rafter length from eaves to ridge, two slopes, pitched at 22.5°. Being recovered in interlocking concrete tiles, 420 × 330mm, 300mm cover width, 75mm headlap.
Roof area: 8.4 × 4.2 × 2 = 70.56m²
Gauge: single-lap tile, so 420 − 75 = 345mm
Tiles per m²: (1000 ÷ 345) × (1000 ÷ 300) = 9.7
Tiles before wastage: 70.56 × 9.7 = 682
Add 5% wastage: 716 tiles
At around £1.70 per tile in 2026, that's roughly £1,217 for the covering, before ridge tiles, battens, membrane and fixings.
Now run the same roof in plain tiles at 60.6 per m²: 70.56 × 60.6 = 4,276, plus 5% is 4,490 tiles. Same roof, same area, 4,490 tiles instead of 716.
That difference doesn't stop at the tile order. Six times the tiles means six times the handling, a lot more labour, and a meaningfully heavier roof. Plain tiles typically load a roof at around twice the dead weight of interlocking concrete per square metre, which is a structural question, not a purchasing one. If you're switching covering type on an existing roof, the tile count is where the conversation starts, not where it ends.
The takeaway: the covering decision and the quantity decision are the same decision. Price them together.
What roofers actually do with the number
In practice, most roofers I've dealt with don't order the exact figure. They add their 5%, then round up to the next full pack, because merchants rarely split packs and the argument isn't worth having over four tiles. The spares end up in the loft, which is precisely where you want them the first time a storm cracks a tile and the product has been discontinued.
The other thing that happens on real jobs: the gauge gets adjusted on site to land the courses evenly between eaves and ridge, rather than leaving a stupid cut course at the top. That means the actual gauge often comes in slightly tighter than the maximum, which nudges the tile count up by a percent or two. Your 5% wastage usually absorbs it. If you calculated at maximum gauge with zero wastage, it won't.
The takeaway: order to the pack, not to the tile, and let the wastage allowance carry the site adjustment.
Getting your own figure
If you want to skip the arithmetic, the Roof Tile Calculator does all of the above. Pick a tile type or enter your own dimensions, add your roof size, and it returns gauge, tiles per m², and a total order figure with wastage.
If you're setting out battens from that gauge, the Roof Batten Spacing Calculator takes it from there. If you don't know your pitch yet, start with the Roof Pitch Calculator — how to calculate roof pitch covers all four measuring methods in detail — and if you need the eaves-to-ridge measurement from a span, the Rafter Length Calculator will give it to you.
Worth noting for anyone who landed here from a search about tiling: this article is about roof tiles. If you're tiling a floor or a wall, how many tiles do I need is the one you want, and the maths is completely different.