Grout Calculator

Joints are normally filled the full depth of the tile.
The default, 98.46 lb/ft3, is the density implied by MAPEI’s published coverage table for Ultracolor Plus FA. Replace it with your own product’s figure if you have one.
Add your own allowance for mixing losses and clean-up; 5-10% is common.
Bags to buy
1
Grout Calculator
Grout needed
2.91 kg
Grout needed
6.41 lb
Grout volume
1.844 L
Grout volume
112.5 in3
Coverage per bag
390.0
Grout per unit of tiled area
1.1250
Grout volume, exact grid geometry
1.815 L
Share of the surface that is joint
2.05 %
Bags needed before rounding up
0.26
Area unit
square feet
Worked out from Grout joint geometry (derivation) and 1 other source.
No waste allowance is included. Most tilers add 5-10% for mixing losses and clean-up.
Grout density varies by product and colour. Check your bag’s own coverage chart before ordering.
An estimate for ordering. Real coverage varies with tile flatness and lippage, the actual joint width achieved, how much is lost in mixing and clean-up, and whether joints are filled full depth. Check your product’s own coverage chart and buy a margin, and treat this as a shopping list rather than a specification.

How this is worked out

5 steps
  1. Grout per unit area = ((L + W) / (L x W)) x joint width x joint depth = 198.438 cm3 per m2 of tiling.
  2. Over 9.29 m2 that is 1.844 litres of grout.
  3. At 1577.2 kg/m3 that weighs 2.91 kg (6.41 lb).
  4. One 25 lb bag covers about 390 sq ft.
  5. Bags needed = 0.26, rounded up to 1.

Results are general information, not financial, tax, legal, medical or engineering advice.