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Project guide

How many tiles do I need, and how much adhesive and grout?

Work out the area, divide by the size of one tile and add 10% for cuts. Adhesive and grout depend on where you are tiling and the joint size.

Updated Based on manufacturer guidance, sources below

The short answer

Tiles = area / area of one tile, plus 10% (15% for diagonal or herringbone). For a 6 m² shower wall in 600 x 300mm tiles that is 37 tiles, about 16.5kg of adhesive (one 20kg bag for a solid bed in a wet area) and about 1.3kg of grout with 3mm joints.

The formula

  • Tiles = area / (tile length x tile width) x 1.10 (1.15 for diagonal or herringbone)
  • Adhesive (kg) = area / coverage x 1.1; coverage is about 0.5 m² per kg on dry walls, 0.4 on wet walls (solid bed), 0.26 on floors
  • Grout (kg) = area x (L + W) / (L x W) x joint width x tile thickness x 1.6, plus 10% (all in mm)

Worked example

A 6 m² shower wall in 600 x 300 x 8mm tiles with 3mm joints:

  • One tile: 0.6 x 0.3 = 0.18 m², so 6 / 0.18 = 33.3, plus 10% = 37 tiles
  • Adhesive, wet wall, solid bed: 6 / 0.4 = 15kg, plus 10% = 16.5kg, so one 20kg bag
  • Grout: 6 x 900 / 180,000 x 3 x 8 x 1.6, plus 10% = 1.3kg

Work it out for your job

Change the measurements and the quantities update straight away.

Length x height for walls, length x width for floors. Take off large windows and doors.
Tiles
37 (6.60 m² if sold by the m²)
Adhesive
16.5 kg, so 1 x 20kg bag
Grout
1.3 kg
Allowance
10% for cuts and breakages
Compare tile adhesive prices

SmartBuild has no tiling project yet, so this opens a search for tile adhesive with live prices. Tiles themselves vary too much to price for you.

Materials checklist

  • TilesBuy from one batch so the shade matches, with 10% spare for cuts.
  • Tile adhesiveFlexible cement-based adhesive for floors, wet areas and underfloor heating.
  • GroutMatched to your joint width. Flexible or water-resistant grout in showers.
  • Tile spacers or levelling clipsKeep joints even. Levelling clips help with large tiles.
  • Silicone sealantAt internal corners, around baths and trays, and where tiles meet other materials.
  • Tanking kit (wet areas)Waterproofs plaster or plasterboard behind tiles in showers.
  • PrimerFor some backgrounds, as the adhesive maker specifies.

You'll also need

  • Notched trowel (6mm for walls, 10 to 12mm for floors and large tiles)
  • Tile cutter, and nippers or an angle grinder for awkward cuts
  • Spirit level, straight batten and pencil
  • Grout float, sponge and bucket
  • Mixing paddle and drill

Step by step

  1. Measure the areaMeasure each wall or floor area in m² and add them up.
  2. Count the tilesDivide by the area of one tile and add 10%, or 15% for diagonal or herringbone patterns.
  3. Choose the adhesiveFlexible cement-based adhesive for floors and wet areas; check the coverage for your trowel.
  4. Set out and fixFix a batten for the first row, spread adhesive with a notched trowel and press the tiles in with spacers.
  5. Grout and sealGrout when the adhesive has set, clean off, then seal corners and edges with silicone.

Tips from the manufacturers

  • BAL gives Rapid-Flex One coverage as about 0.5 m² per kg on dry walls (6mm notch), 0.4 m² per kg for a solid bed on wet walls and 0.26 m² per kg on floors (10mm notch). A 20kg bag therefore does about 10, 8 or 5 m².
  • British Gypsum allows tiles up to 20kg per m² directly onto Thistle finishing plasters, with a lower limit where a bonding agent was used. For heavy tiles, tile straight onto the background or board.
  • In showers, BAL recommends waterproof tanking over plaster or plasterboard and a solid bed of water-resistant adhesive.
  • Back-butter large-format tiles and use a bigger notch so there are no hollow spots.

Mistakes to avoid

  • Buying exactly the area with nothing spare, then finding the next batch is a different shade.
  • Using ready-mixed tub adhesive on floors or in showers when the tub says walls only.
  • Spot-fixing tiles with dabs of adhesive, which leaves voids that crack or hold water.
  • Tiling onto fresh plaster or screed before it has dried.

Frequently asked questions

How many tiles do I need for 1 m²?

For 300 x 300mm tiles, about 11.1 per m², or about 12.2 with 10% spare. For 600 x 300mm, about 5.6 per m², or about 6.1 with 10%.

How much tile adhesive per m²?

It depends on the trowel and bed. From BAL's figures, about 2kg per m² on dry walls, 2.5kg per m² for a solid bed on wet walls, and about 3.8kg per m² on floors with a 10mm notch.

How much grout do I need?

It depends on tile size, joint width and tile depth. For 600 x 300 x 8mm tiles with 3mm joints, about 0.2kg per m². Small tiles and wide joints need much more.

How much extra tile should I buy?

10% for straight or brick-bond layouts, 15% for diagonal or herringbone, and a little more if there are lots of cuts or the tiles are fragile.

Can I tile straight onto plaster?

Onto dry, sound Thistle finishing plaster, British Gypsum allows tiles up to 20kg per m². In wet areas, tank the wall first.

Sources

Quantities are estimates for typical jobs, using the coverage figures above. Products vary, so check the data sheet for the product you buy, and talk to a professional for structural, electrical or gas work. SmartBuild is independent and not affiliated with any of the manufacturers listed.

How much plaster do I need to skim a room?A finish skim is about 2mm thick. British Gypsum says a 25kg bag of Multi-Finish covers about 10 m² at that thickness. How much plasterboard do I need?Each standard 2400 x 1200mm sheet covers 2.88 m². Divide your area by that, add 10% for cuts, then work out the screws, tape and plaster to go with it. How much sand and cement do I need for bricks, blocks or slabs?Work out the volume of mortar first, then split it into cement and sand by the mix. Here are the standard UK rates for brickwork, blockwork and laying paving slabs.

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