Grout calculator
The smaller the tile, the more grout you need.
Your inputs
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Example loaded. You can change any value.
There is no figure yet: nothing is calculated until you ask for it.
- Enter your measurements.
- Check the units and the assumptions.
- Press Calculate, or load the example.
Rather see a worked case? Press “Load example” and change any value afterwards.
Next step
Corners and junctions are not filled with grout but with sealant.
Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates
How to use it
- Enter the tiled area.
- Give the tile size and its thickness.
- Set the joint width you will leave.
- If you buy in bags, enter the bag weight.
How it is calculated
Grout fills the gap between tiles. The volume of that gap per square metre depends on the perimeter of each tile, not its area:
Which leads to something surprising: the smaller the tile, the more grout you need. A 2 x 2 in mosaic uses six times as much as a 12 x 12 in tile with the same joint, because there are six times more linear metres of joint.
The default density (1,600 kg/m³) is that of a conventional cement grout. Epoxy grouts weigh slightly more and behave differently; check the data sheet if you use one.
Worked example
A 108 sq ft floor with 12 x 12 in tiles, 8 mm thick, 2 mm joints:
- Volume per m²: 0.0001067 m³
- Consumption: 0.171 kg per square metre
- Total with 10 % waste: 1.88 kg (about 4 lb)
Under two kilos for a hundred square feet. The same area in 2 x 2 in mosaic would need more than 11 kg.
Good to know
- Tile thickness counts. A 2 mm joint in a 12 mm tile uses 50 % more grout than in an 8 mm one.
- Wide joints, different product. Above 6 mm you normally need a sanded grout rather than a fine one.
- Buy a whole bag. Grout comes in 1, 5 or 25 kg bags; having half a kilo left over is normal and useful for touch-ups.
- Mix in one go. Preparing grout in two separate batches can leave visible shade differences once dry.
Frequently asked questions
How much grout do I need per square foot?
With 12 x 12 in tiles, 8 mm thick and 2 mm joints, about 0.016 kg per square foot (0.17 kg per m²). With a 2 x 2 in mosaic, more than six times that. Tile size is the dominant factor.
Why does mosaic use so much grout?
Because consumption follows the linear metres of joint per unit area. Small tiles mean vastly more joints for the same floor.
How wide should the grout joint be?
1.5 to 3 mm for rectified indoor tiles, 3 to 6 mm for non-rectified or outdoor tiles. Too fine a joint leaves no room for substrate movement.
Is epoxy grout calculated the same way?
The volume, yes; the weight can differ because the density is different. If you use epoxy, enter the manufacturer's density in the advanced options.