Why do small tiles need so much more grout?

Because grout sits in the joints and small tiles have far more joint length per square metre. Halving the tile size roughly doubles the grout.

Construction & Homefinishing

Tile Grout Calculator

Grout quantity from tile size, joint width and thickness. Smaller tiles need far more grout because there is more joint per square metre.

Also called: tile grout quantity.

Grout (kg)

3.31

3.31 kg for 20 m² with 3mm joints, which is 0.14 kg per square metre.

Kg per square metre

0.14

Joint volume (litres)

2.07

In 5 kg bags

0.66

How this is calculated

Method and background

How this is calculated

The joint volume per square metre falls as tiles get larger, since a 600mm tile has a fifth of the joint length of a 100mm mosaic. Multiply the joint volume by grout density, around 1,600 kg per cubic metre, and add wastage for what stays in the bucket and the float.

grout per square metre depends on tile size, joint width and tile thickness

l, w: Tile length and width (mm)
j: Joint width (mm)
t: Tile thickness (mm)

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

large tiles use little grout

Tiled area (m²): 20
Tile length (mm): 600
Tile width (mm): 600
Tile thickness (mm): 9
Joint width (mm): 3
Wastage: 15%

Grout (kg)3.31

(600+600)/(600*600) * 3 * 9 * 1.6, worked by hand

Open this example

small tiles use far more

Tiled area (m²): 20
Tile length (mm): 100
Tile width (mm): 100
Tile thickness (mm): 6
Joint width (mm): 3
Wastage: 15%

Grout (kg)13.25

boundary: four times the grout for a sixth the tile

Open this example

Method and limits

What it assumes

Joints filled to the full tile thickness, and grout density of 1,600 kg/m³.

What it deliberately does not model

Epoxy grout is denser and behaves differently. Uneven substrates use more.

Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator

Frequently asked questions

Why do small tiles need so much more grout?: Because grout sits in the joints and small tiles have far more joint length per square metre. Halving the tile size roughly doubles the grout.