Grout Calculator

How much grout you need: tile size, joint width and depth, and the area give pounds or kilograms of grout and the number of bags.

Grout fills the joints between tiles, so the amount depends on how long the joints are, how wide and how deep. Tile and grout makers use the same formula: kg per m² = (tile length + tile width) ÷ (length × width) × joint width × joint depth × density, with sizes in millimetres and a density of about 1.6 kg per litre for cement-based grout. For 300 × 300 mm tiles 8 mm thick with 3 mm joints, that's 0.256 kg per m². Small tiles have far more joint per square metre, so mosaics and subway tiles take much more grout than large slabs. Enter your area, tile size and joint, and the calculator gives the grout in pounds or kilograms and the number of bags.

Units
Area
ft
ft
Feet and inches work too: type 12'6 or 12.5.
in
in
in
in
%
Grout
5.72 lb

2.6 kg

Bags
1

10 lb bag

Per 100 ft²
6.5 lb

before extra

How it was worked out
  1. Area: 10 ft × 8 ft = 80 ft²
  2. (304.8 + 304.8) ÷ (304.8 × 304.8) × 3.18 mm joint × 9.52 mm deep × 1.6 kg/L = 0.318 kg per m²
  3. 0.318 kg/m² × 7.43 m² × 1.1 = 5.72 lb; ÷ 10 lb bag = 1 bag

The formula is the one grout makers publish, with a density of about 1.6 kg per litre for cement-based grout. Epoxy and other grouts differ, so check the bag's coverage table.

Common use cases

  • Buy grout for a new floor or wall
  • Compare the grout needed for small and large tiles
  • Regrout an old shower or splashback
  • Check a tile shop's estimate

How to use

  1. Enter the tiled area.
  2. Enter the tile length and width, the joint width and the joint depth (usually the tile thickness).
  3. Keep the density at 1.6 for cement-based grout, or use the figure from your product.
  4. Choose a bag size and read the grout and bags needed.

FAQ

How much grout do I need per square foot or square metre?

It depends on the tile size and joint. For 12 × 12 in tiles with 1/8 in joints 3/8 in deep, about 0.32 kg per m², or roughly 6.5 lb per 100 ft². For small mosaics with the same joints, several times as much.

Sanded or unsanded grout?

Unsanded grout is generally used for joints narrower than about 1/8 in (3 mm), and sanded grout for wider joints, where the sand stops it shrinking and cracking. Always follow the tile and grout maker's recommendations.

Does epoxy grout use the same amount?

The volume of joint is the same, but epoxy grouts have a different density and are sold by weight in kits, so check the product's coverage table. Adjust the density in the calculator to match.

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