Ceramic & Stone Tile Calculator

Q: How many tiles do I need per square metre?

Divide 1 m2 by the area of one tile (length x width in metres). A 600 x 300 mm tile covers 0.18 m2, so you need 1 / 0.18 = 5.56 tiles per m2 - round up to 6. For a 20 m2 floor at 6 tiles per m2, you need 120 tiles before waste. Add 10% waste for a straightforward square room with few cuts, or 15% for diagonal layouts, L-shaped rooms, or rooms with many fixed obstacles.

Q: What tile adhesive and grout do I need?

For wall tiles on a standard plasterboard or plaster background, use a ready-mixed tile adhesive or powder adhesive at approximately 2-3 kg/m2. For floor tiles on a solid or screed background, use a flexible floor tile adhesive at approximately 3-5 kg/m2 depending on the tile size and back profile. Larger format tiles (over 300 x 300 mm) require a larger-format adhesive with good non-slip properties. For grout, allow approximately 0.5-1 kg per m2 depending on tile size and joint width.

Q: What grout joint width should I use for floor tiles?

Grout joint width depends on the tile type and size. For ceramic and porcelain tiles, a minimum 2-3 mm joint is standard for wall tiles and 3-5 mm for floor tiles. For natural stone, larger 5-10 mm joints are typical to accommodate natural size variation. Rectified tiles (precisely cut to exact dimensions) can be laid with a 2 mm joint. Never butt-joint tiles with no grout gap as thermal movement will cause cracking. Manufacturer recommendations should always take precedence.

Q: What substrate do I need under floor tiles?

Floor tiles require a solid, stable, and level substrate. Concrete or sand-cement screed is ideal. Timber joisted floors require a stiff decking board (minimum 18 mm plywood or tile backer board) to prevent flexing, which can crack grout and tiles. Timber floors should have a maximum deflection of L/360 (where L is the joist span) before tiling. Backer boards such as Hardiebacker or Wedi provide a rigid, moisture-resistant surface. Do not tile directly onto chipboard or OSB.

Q: What Building Regulations apply to tiling in wet rooms and shower enclosures?

UK Building Regulations Approved Document C requires wet areas such as shower enclosures and wet rooms to be fully waterproofed to prevent moisture penetrating to the structure. A tanking system (waterproof membrane applied before tiling) or a waterproof tile adhesive and grout system approved for wet zones must be used. Shower trays and wet room floors must slope to the drain at a minimum 1:80 fall. Tiles in shower areas must also have a slip resistance rating appropriate for wet conditions - minimum R9 or R10 for wet floor areas.

Q: What waste allowance should I use for tiles?

Allow 10% waste for a straightforward square or rectangular room with tiles laid parallel to the walls. Use 15% for L-shaped rooms, rooms with many fixed obstacles (toilets, baths, kitchen units) or for large-format tiles where cuts are more wasteful. Use 15-20% for diagonal or pattern layouts. Natural stone tiles should have 15% minimum as they can vary in size and some will need to be discarded for colour or texture reasons. Always buy from the same batch (same shade code) and keep a few spare tiles for future repairs.

How many tiles do I need per square metre?

Divide 1 m² by the tile area (length x width in metres) to get tiles per m². A standard 600 x 300 mm tile covers 0.18 m², so you need 1 ÷ 0.18 = 5.56 tiles per m² - round up to 6. Multiply by your room area and add 10% waste for a straightforward room with few cuts, or 15% for diagonal layouts and rooms with many obstacles. For wet rooms and shower enclosures, UK Building Regulations Approved Document C requires the substrate and tile fixing system to be fully waterproofed - use a tanking system or waterproof adhesive and grout rated for wet zone applications.

Ceramic & Stone Tile Calculator

Add each area, set tile size and grout joint, and get tile count, packs, grout and adhesive

Metric (m) Imperial (ft / in)

Areas

Common Tile Sizes

Tile Width (mm)

Tile Height (mm)

Grout Joint Width (mm) Rectified / porcelain: 2-3mm • Standard ceramic: 3-5mm • Natural stone: 5-10mm

Lay Pattern

Waste Factor (%)

10%

Standard straight lay - increase for diagonal (15%) or complex patterns (20%)

Tiles per Pack (optional) Leave blank to get tile count only

Grout & Adhesive

Optional - enter coverage rates and costs from your product packaging.

Grout coverage (m² per kg) Check your grout packet - coverage varies by tile size and joint width

Grout bag size (kg)

Grout cost per bag

Adhesive coverage (m² per bag) Typically 3-5 m² per 20kg bag depending on tile size and adhesive type

Adhesive bag size (kg)

Adhesive cost per bag

Job Costing

Enter costs in your local currency.

Cost per tile

UK Market PricesFills in the material cost fields with current UK market prices. You can review and edit each price before applying.

Results

Total Area
-
m²

Tiles to Order

inc. waste

Packs to Order

packs

Grout Needed

bags

Adhesive Needed

bags

Area Breakdown

Area	Floor / Wall Area	Area + Waste	Tiles	Packs

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Frequently Asked Questions

How many tiles do I need per square metre?

Divide 1 m² by the area of one tile (length x width). A 600 x 300 mm tile covers 0.18 m², so 1 ÷ 0.18 = 5.56 tiles per m² (round up to 6). Add 10% waste for a straightforward room; 15% for diagonal layouts, L-shaped rooms, or rooms with many fixed obstacles.

What tile adhesive and grout do I need?

Wall tiles on plaster: 2-3 kg/m² ready-mixed or powder adhesive. Floor tiles on screed: 3-5 kg/m² flexible floor tile adhesive (more for large formats). Large format tiles (over 300 x 300 mm) need a non-slip, large-format adhesive. Grout: approximately 0.5-1 kg per m² depending on tile size and joint width.

What grout joint width should I use for floor tiles?

Ceramic/porcelain wall tiles: minimum 2-3 mm joint. Floor tiles: 3-5 mm. Natural stone: 5-10 mm to accommodate size variation. Rectified tiles can be laid at 2 mm. Never butt-joint with no gap - thermal movement will crack grout and tiles. Always follow the manufacturer's recommendation.

What substrate do I need under floor tiles?

Tiles need a solid, stable, level substrate. Concrete or sand-cement screed is ideal. Timber joisted floors need minimum 18 mm plywood or tile backer board (Hardiebacker, Wedi) to prevent flex that cracks grout. Maximum deflection L/360 before tiling. Do not tile directly onto chipboard or OSB.

What Building Regulations apply to tiling in wet rooms and shower enclosures?

Approved Document C requires wet areas to be fully waterproofed. Use a tanking system or waterproof adhesive/grout approved for wet zones. Wet room floors must slope to drain at minimum 1:80 fall. Floor tiles in wet areas need minimum R9 or R10 slip resistance rating for wet conditions.

What waste allowance should I use for tiles?

Simple rectangular room, parallel lay: 10%. L-shaped rooms, many obstacles, or large-format tiles: 15%. Diagonal or pattern layouts: 15-20%. Natural stone: minimum 15% due to size and colour variation. Always buy from the same batch and keep a few spare tiles - shade codes change and discontinued tiles are impossible to match.

Tile Types Guide

Ceramic - Fired clay with a glazed surface. Lighter and easier to cut than porcelain. Best for walls and light-traffic floors.
Porcelain - Dense, low-absorption tile. Suitable for floors, wet rooms and external use. Requires a diamond blade to cut.
Natural stone - Marble, travertine, slate, limestone. Needs sealing. Use a flexible adhesive and wider grout joints.
Mosaic - Small tiles on mesh sheets. Measure the sheet area, not individual tiles. Allow 15%+ waste.
Encaustic / cement - Patterned unglazed tiles. Seal before grouting to prevent staining.

Grout Joint Guide

Rectified / porcelain - 2-3mm. Precise factory-cut edges allow very tight joints.
Standard ceramic - 3-5mm. Slight size variation means a wider joint is needed.
Natural stone - 5-10mm. Irregular edges and movement allowance.
Mosaic sheets - 2-3mm between tiles; 5mm between sheets.

Use an unsanded grout for joints under 3mm, sanded grout for 3mm and above.

Pattern Waste Guide

Straight lay - 10% waste. Most efficient, minimal cuts.
Brick bond / offset - 10-12% waste. Staggered joints like brickwork.
Diagonal (45°) - 15% waste. Every border tile needs a diagonal cut.
Herringbone - 15-20% waste. High cut rate at each end of the pattern.

Always buy at least one extra box and keep it for repairs - matching a discontinued batch is very difficult.

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Ceramic & Stone Tile Calculator

How many tiles do I need per square metre?

Ceramic & Stone Tile Calculator

Areas

Grout & Adhesive

Job Costing

Results

Area Breakdown

Cost Estimate

Frequently Asked Questions

Tile Types Guide

Grout Joint Guide

Pattern Waste Guide

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