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Randozi
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Tile Grout Calculator

Buy the right amount of grout the first time: the volume of your joints is worked out from the tile size, the joint width and the depth.

Grout to buy

2.77 kg

1 bag of 5 kg. 2.52 kg without the waste allowance.

Joints share of surface

1.97 %

Volume of joints

1.58 L

Per m²

0.25 kg

Tiles to buy

Uses the area above. Tiles are sold by the carton, so the count is rounded up.

Tiles to buy

8 cartons

10 m² + 10% loss = 11 m² needed. One carton covers 1.44 m², so you get 11.52 m² (0.52 m² spare).

How it works

  1. Type the tile length and width in millimetres, and the joint width between tiles.
  2. Enter the tile thickness, which is the depth the grout fills, and the area to tile in square metres.
  3. Check the density and bag size: the defaults are common values, so replace them with the figures on your product.
  4. Read the kilograms needed with your waste allowance and the number of bags to buy. Under the fields, add the tile loss and what one carton covers to get the number of tile cartons.

What people use it for

  • Bathroom floor

    Estimate the grout for 6 m² of 300 × 300 mm tiles with 3 mm joints.

  • Mosaic or small tiles

    See how quickly the amount grows when tiles get smaller and joints take a larger share.

  • Comparing joint widths

    Find out how much more a 5 mm joint needs than a 2 mm joint on the same wall.

Questions

How is the quantity computed?
Each tile sits in a cell of (length + joint) × (width + joint). The joints are what remains of that cell around the tile, so their share of the surface is 1 − (length × width) ÷ ((length + joint) × (width + joint)). Multiply by the area and the depth to get litres, then by the density to get kilograms.
Which density should I use?
The default of 1.6 kg per litre is a typical figure for a powder cement grout once mixed and set, but products differ. Use the consumption or density printed on your bag when you have it; the result scales directly with it.
Why add a waste allowance?
Some grout stays in the bucket, on the sponge and in uneven joints, and tile edges are rarely perfect. 10 % is a common allowance; the tool rounds the bags up so you do not run out halfway.
How is the number of tile cartons worked out?
Cartons = area × (1 + loss ÷ 100) ÷ the area one carton covers, rounded up to a whole carton. For 10 m² with a 10 % loss and cartons of 2 m², that is 11 ÷ 2 = 5.5, so 6 cartons. The loss is separate from the grout waste allowance. Check the coverage printed on your box, and keep a few spare tiles from the same batch because colours can vary between batches.