Roof Tile Calculator: Tiles Per Square Metre by Profile, Plus Waste, Ridge and Valley

Quick Answer: For a typical UK pitched roof, allow approximately 9.7 plain tiles, 9.5 plain double-camber tiles, 16 large interlocking concrete tiles, or 22 small Roman/pantile tiles per square metre — then add 7–10% waste, 12–15% on cut-heavy hipped or valley roofs, plus 1.05 ridge tiles per linear metre and 3 valley tiles per linear metre. Always cross-check the manufacturer's gauge tables, since tile count varies with batten gauge across pitch ranges.

Summary

A roof tile take-off is a textbook arithmetic job that gets miscalculated more often than you'd think. The wrong tile-per-m² figure on a 220m² roof can produce a 1,500-tile underorder — a week's delay, two extra deliveries, and a relationship-damaging change-order conversation. A 15% over-order ties up cash and floods a builders' merchant return queue.

This guide gives the tile-per-m² density for every common UK profile (plain, large interlocking concrete, Roman pantile, slate, fibre cement slate, clay pantile), the gauge tables that link batten centres to coverage, the waste percentages by roof complexity, and the per-linear-metre allowances for ridge, hip, and valley. It includes worked examples for a typical 3-bed semi and for a more complex T-plan with two valleys.

The biggest single error in DIY take-offs: using the manufacturer's "headline" coverage figure without checking the actual minimum pitch/maximum gauge for the project. A tile rated "9.6/m² at 100mm headlap" only delivers that density at the headlap to 30°. At 22.5° pitch it might require 75mm headlap and the density rises to 10.4/m² — five extra tiles per square metre, hundreds across a roof.

Key Facts

Quick Reference Table — Tiles per m²

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Tile Profile Size Tiles/m² Min Pitch Headlap
Plain tile 265×165mm 60 35° (40° preferred) 65mm typical
Large interlocking 420×330mm 9.7 17.5°–22.5° 75mm
Mendip / small interlocking 387×229mm 13.5 25° 75mm
Roman pantile 420×330mm 14.5 22.5° 75mm
Double Roman 420×330mm 9.5 17.5° 75mm
Clay pantile 343×270mm 18 30° 75mm
Spanish slate 500×250mm 21 25° 75mm
Spanish slate (low pitch) 500×250mm 24 22.5° 100mm
Welsh slate 500×250mm 21 22.5° 75mm
Fibre cement slate 600×300mm 13.5 20° 90mm
Stone slate (random) varies varies — typically 100kg/m² 33° 100mm random sizing

Detailed Guidance

Step 1 — calculate the roof area

For a duo-pitched roof with no hips:

Roof area = (eaves length × rafter length) × 2 sides
Rafter length = √((span/2)² + height²)
            = (span/2) ÷ cos(pitch°)

Worked example — a 3-bed semi with 8.0m eaves, 6.5m span, 35° pitch:

For a hipped roof (4-sided), area calculation is the same — the hip rafters create triangular ends that combine to the same total m² as the gable equivalent. The cuts and waste percentage rise; the m² doesn't.

Step 2 — apply the tile/m² density

Using a large interlocking concrete tile at 9.7 tiles/m²:

But this assumes flat plain area only. Add ridge, hips, valleys, verges separately.

Step 3 — add ridge, hips, valleys, verges

For a typical 3-bed semi gable roof:

For a hipped roof with one front hip:

Step 4 — apply waste

Roof Complexity Waste %
Simple gable, no hips/valleys 5–7%
Standard gable with one chimney 7–10%
Hipped roof 10–12%
Hip + valley combination 12–15%
L-plan with two valleys 14–18%
Complex roof, multiple intersections 18–22%

Adding 10% to our 616-tile gable roof: 616 × 1.10 = 678 tiles

Step 5 — match the manufacturer's gauge table

Every manufacturer publishes a gauge table for their tile, e.g.:

Pitch Headlap Gauge (batten centres) Tiles/m²
17.5° 100mm 318mm 10.4
22.5° 100mm 318mm 10.4
22.5° 90mm 328mm 10.0
30° 75mm 343mm 9.7
45° 75mm 343mm 9.7

Always use the table for the actual pitch and the minimum headlap allowed. A 22.5° pitch needs 90–100mm headlap on this tile and rises to 10.4 tiles/m² — a 7% increase over the 30° figure. Pricing or ordering off the wrong row produces undersupply.

Worked example — T-plan house with two valleys

Property: rear extension creating a T-plan with two valleys.

Total order: 1,146 tiles + 14 ridge + 26 valley + 9 verge + 8.4m valley liner

Step 6 — battens and underlay (count alongside tiles)

Tile order without batten and underlay take-off is incomplete. The same gauge that determines tile-per-m² determines batten quantity:

Example: 103.6m² roof needs 103.6 × 1.05 (waste) = 109m² underlay. A 1.5m × 50m roll = 75m² effective after laps = 1.5 rolls (round up to 2).

For homeowners — what should the tile order cost?

Tile cost per m² for materials only (no labour, no battens, no underlay):

Add £15–£25/m² for battens, underlay and fixings; £30–£55/m² for labour; total fitted £75–£280/m² depending on tile choice. See the full pitched roofing materials and labour breakdown for installed pricing.

Frequently Asked Questions

How much waste should I budget for a hipped roof?

10–15% is the standard band. Hips create cut tiles along both pitches that meet at the hip rafter, and many of those cuts produce small offcuts that can't be reused. Single hip = 10–12%; two hips on an L-plan = 12–15%. Add another 2–3% for concealed valleys or chimneys.

Why do manufacturers list more than one tile/m² figure for the same tile?

Tile coverage depends on the headlap, which depends on the pitch. Lower pitch = bigger headlap = more tiles per m². A tile listed as "9.7/m²" usually shows that density at maximum gauge (minimum headlap, around 75mm) for steeper pitches. Use the manufacturer's gauge table to read the correct density for your specific pitch.

Should I order ridge tiles by the number or the metre?

By the number, calculated from the linear metre run × 1.05. Ridge tiles are usually 300–450mm long and overlap 30–50mm at each joint. The 1.05 multiplier covers a 300mm tile with 15mm overlap each side. For longer 450mm ridge tiles use 0.7/m × 1.05 = 0.74/m.

Do I need to count tile-and-a-half tiles separately?

Yes for plain tile roofs. Tile-and-a-half tiles maintain the bond at every other course on a gable verge — without them, the bond breaks at the verge and the roof aesthetic and rain-shedding both suffer. One tile-and-a-half per course of plain tile run on the gable, so for a 4m-rafter gable at 100mm gauge that's 40 courses × 2 sides ≈ 80 tile-and-a-half tiles. Most builders' merchants stock these alongside the standard tile.

What's the difference between a valley tile and a valley liner?

A valley tile (purpose-made bonnet hip valley tile, found on plain-tile roofs) is a manufactured tile that runs along the valley line covering the join. A valley liner (lead, GRP or formed metal sheet) is a continuous waterproof tray laid in the valley with cut tiles dressed over each side. Plain tile roofs use bonnet valleys; interlocking tile roofs use lead-lined valleys (Code 5 typical).

Regulations & Standards