What it works out
This works out how much grout and tile adhesive a tiling job needs, in kilos and bags, and how much sealant to finish the edges, in cartridges.
It uses the same formulas the manufacturers publish, so you can check the figure on the bag against your own job.
How it works
Grout fills the joints between tiles, so it depends on how much joint there is. Small tiles have more joint per square metre than large ones. The calculator works out the volume of the joints from the tile size, the joint width and its depth (usually the tile's thickness), and turns it into kilos with a cement grout's density.
Adhesive depends on the bed: how thick it is once the tiles are pressed in. The calculator multiplies the area by the bed's thickness and the density of a powder adhesive.
Sealant is worked out from the length to seal, such as round a bath or a shower tray, as a square bead of the width you choose, and turned into cartridges. The waste allowance applies to all three.
A worked example
6 m² of tiles 30 cm by 60 cm, with 3 mm joints 8 mm deep, fixed on a 3 mm bed of adhesive.
- Grout: 6 m² × (30 cm + 60 cm) ÷ (30 cm × 60 cm) × 3 mm × 8 mm × 1,600 kg/m³ = 1.15 kg
- Grout: 1.15 kg + 10% for waste = 1.27 kg → 1 bag of 2.5 kg
- Adhesive: 6 m² × 3 mm × 1,500 kg/m³ for a powder adhesive = 27 kg
- Adhesive: 27 kg + 10% for waste = 29.7 kg → 1 bag of 20 kg + 1 bag of 10 kg
The result
- Grout1.27 kgBuy 1 bag of 2.5 kg (2.5 kg)
- Tile adhesive29.7 kgBuy 1 bag of 20 kg + 1 bag of 10 kg (30 kg)
These are the calculator's own figures for these measurements, with 10% for waste. Change any of them above and it works it out again.
Common mistakes
- Using the same grout figure for every tile. Mosaics and small tiles take several times more grout per square metre than large tiles. Work it out for your tile.
- Underestimating the bed. Large floor tiles and uneven floors need a thicker bed. The notch size of your trowel decides the bed, so check the adhesive bag's table.
- Grouting where it should flex. Corners where walls meet, and joints against a bath or tray, move. Seal them with silicone, not grout.
- Mixing too much at once. Grout and adhesive have a working time. Mix only what you can use before it starts to set.
Questions people ask
How much grout do I need per square metre?
It depends on the tile size, the joint width and its depth. Small tiles with wide joints take the most. Enter your tile and joint and the calculator gives the weight for your area.
How much tile adhesive do I need?
Multiply the area by the bed thickness and the adhesive's density. A thin wall bed takes far less than a thick floor bed under large tiles. The bag usually gives its own rate per millimetre.
How deep is a grout joint?
Usually the full thickness of the tile, less any adhesive squeezed up between them. Rake out the joints before the adhesive sets so the grout can fill them.
How many cartridges of sealant do I need?
Measure the length to seal and choose the bead's width. The calculator turns that into a volume and divides by the cartridge size, adding the waste allowance.
Does epoxy grout work the same way?
The volume of the joints is the same, but epoxy grouts have a different density and come in kits. Use the joint volume from the working and the maker's coverage table.