How many roof tiles do I need per m²?

It depends on the tile type. Clay plain tiles (265×165mm): approximately 60 per m² with 65mm headlap. Concrete interlocking tiles (420×330mm): approximately 10.5 per m² with 75mm headlap. Natural slate (500×250mm): approximately 20 per m² with 100mm headlap. Our calculator works out the count from tile dimensions and headlap.

How do I calculate roof tile gauge?

For single-lap interlocking tiles: gauge = tile length minus headlap. For double-lap plain tiles and slates: gauge = (tile length minus headlap) divided by 2. The gauge is the exposed face of each tile visible on the finished roof. Tiles per m² = (1000 ÷ gauge) × (1000 ÷ tile width).

What size roofing battens do I need?

Standard UK roofing battens are 38×25mm or 50×25mm treated softwood, graded to BS 5534. The batten gauge matches the tile gauge. Batten spacing must be consistent — set out from the eaves batten up. For rafter spacings up to 600mm, 25mm battens are typically sufficient; for wider spacings, 38mm depth may be specified.

How many ridge tiles do I need?

Standard half-round ridge tiles are 450mm long. Count the ridge length and divide by 0.45 (with a small overlap allowance). For a 6m ridge: 6 ÷ 0.45 = approximately 14 ridge tiles. Always add 5% for cutting at hips or valleys.

What is the minimum pitch for roof tiles?

Clay plain tiles: minimum 35° pitch (can be reduced to 30° with increased headlap). Concrete interlocking tiles: typically 17.5°–22.5° minimum depending on model. Natural slate: minimum 20°–25° depending on lap. Always check the manufacturer's specification for your specific product.

Roof Tile & Batten Calculator

Roof Tile Calculator

Calculate roof tiles, ridge tiles, hip tiles and battens from your roof dimensions. Covers clay plain tiles, concrete interlocking, natural slate and large format tiles. BS 5534 batten specification included. 2026 UK pricing.

Last reviewed 15 May 2026

5 tile types

Ridge & hip tiles

BS 5534 battens

Pitch angle check

Rule of thumb: Clay plain tiles (265×165mm) require approximately 60 per m² at 100mm gauge. Concrete interlocking tiles (420×330mm) require approximately 10.5 per m² at 345mm gauge. Standard 450mm ridge tiles cover 0.45m length each. Always allow 10% wastage.

Roof Details

Select tile type and enter roof dimensions

Tile Type

Clay plain tiles: traditional double-lap tile. 65mm headlap standard. Minimum 35° pitch; use 75mm headlap for pitches 30–35°.

Headlap (mm)

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Roof Area Method

Eaves length (m)

Slope length (m)

Eaves to ridge along slope

Number of pitched slopes

Roof features

Wastage Allowance

Roof Tile Estimate

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Roof area

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Field tiles

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Gauge

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mm batten centres

Battens

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linear metres

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Materials to Order

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Estimated total (materials only)

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2026 UK mid-market prices. Excludes underlay, nails, mortar and labour.

BS 5534 Batten specification

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Building Regulations — Part A & L

If changing tile type (e.g. slate to concrete), Part A requires structural check for increased load. Replacing more than 25% of the roof area triggers Part L insulation upgrade requirements. In Conservation Areas and on listed buildings, like-for-like replacement with matching materials is usually required.

For a standard 50 m² duo-pitch roof with concrete interlocking tiles at 75mm headlap, you need approximately 578 tiles and 284m of battens.

Roof Tile Quick Reference

Standard headlaps · 10% wastage · duo-pitch roof

Tile Type	Net /m²	Gauge (mm)	Min pitch
Clay plain tiles	60	100mm	35°
Concrete interlocking	8.8	345mm	17.5°
Natural slate 500×250	20	200mm	20°
Concrete plain tiles	60	100mm	35°
Large format / Marley Modern	8	370mm	12.5°

Gauges and pitches based on standard headlaps. Always verify with tile manufacturer's fixing specification. Plain tiles and slate use double-lap formula: gauge = (length – headlap) ÷ 2. Interlocking tiles use single-lap: gauge = length – headlap.

Technical Guide

Calculating Roof Tiles

Gauge, headlap and the tile calculation

The gauge is the exposed face of each tile — the distance between batten centres. For single-lap interlocking tiles: gauge = tile length − headlap. For double-lap plain tiles and slates: gauge = (tile length − headlap) ÷ 2. The double-lap formula produces a shorter gauge and more tiles per m², which is why plain tiles require 60/m² versus 10.5/m² for large interlocking tiles.

Tiles per m² = (1000 ÷ gauge) × (1000 ÷ tile width). This formula works for any tile size — use the custom option in our calculator for non-standard products.

Battens — BS 5534 specification

Roofing battens must be graded to BS 5534 — this is a mandatory structural requirement. Battens graded to this standard are marked with a blue certification mark and have been tested for strength, durability and moisture resistance. Do not use random timber as roofing battens.

Standard sizes: 38×25mm for rafter spacings up to 600mm; 50×25mm for spacings up to 750mm. Battens should be pressure treated with a minimum preservative to UC3. Set out from the eaves — the first batten sits at the fascia, the second at the gauge distance, and so on up to the ridge.

Ridge tiles, hip tiles and verge tiles

Standard half-round and angular ridge tiles are 450mm long. For a mortar-bedded ridge, allow approximately 5% overlap at joints, giving an effective coverage of ~430mm per tile. For a 6m ridge: 6 ÷ 0.43 = 14 ridge tiles. Dry-fix ridge systems use proprietary components — count units from the manufacturer's specifications.

Hip tiles are typically the same product as ridge tiles. Hip length is calculated from the roof geometry: for a square plan hip roof, hip length = eaves ÷ (2 × cos 45°) × number of hips. Verge tiles (half tiles) are needed at gable ends — count the number of tile courses and order one verge tile per course per gable.

FAQ

Common Questions

How many roof tiles per m²?

Depends on tile type: clay/concrete plain tiles ~60/m², concrete interlocking ~10.5/m², natural slate 500×250mm ~20/m², large format ~8/m². Our calculator derives the figure from tile dimensions and headlap using the gauge formula.

What is the gauge of a roof tile?

The gauge is the exposed face of each tile — the centre-to-centre batten spacing. Single-lap tiles: gauge = tile length − headlap. Double-lap tiles: gauge = (tile length − headlap) ÷ 2. Battens are fixed at every gauge interval from eaves to ridge.

Do roofing battens need to meet BS 5534?

Yes. BS 5534 is a mandatory requirement for roofing battens in the UK. Compliant battens are marked with a blue certification stamp. Non-compliant timber must not be used as it may not have adequate strength or moisture resistance. Most merchant-supplied roofing battens meet this standard, but always check.

How do I measure a roof slope length?

Measure from the eaves (bottom edge) to the ridge (apex) along the actual slope surface — not horizontally. From the ground, you can use a spirit level and tape measure, or calculate from horizontal depth and pitch angle: slope length = horizontal depth ÷ cos(pitch angle). For a 4m horizontal depth at 35° pitch: 4 ÷ cos(35°) = 4.88m slope length.

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