Grout Calculator
Calculate how much grout a tiling job needs from the tile size, joint width and joint depth.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Grout consumption depends on how many joints there are, not just the area. Small tiles create far more joint length than large ones, which is why a mosaic floor needs several times the grout of a large-format floor over the same area. For square tiles, enter the same length and width. Results include joint volume; density is an assumed 1.6 g/cm³ and bag size is 5 kg.
Worked example
calculated with the default values below
Area to tile 100 sq ft · Tile length 12 in · Tile width 12 in · Tile thickness 0.375 in · Joint width 0.125 in Total joint length 200 ft · Grout needed 2.95 kg · Grout needed 6.50 lb · 5 kg bags to buy 1 · Grout volume 112.50 in³
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
G = A×144/(L×W)×(L+W)×2.54³×J×D×1.6/1000
- A
- Tiled area, ft²
- L
- Tile length, in
- W
- Tile width, in
- J
- Joint width, in
- D
- Tile thickness, in
- G
- Grout required, kg
bags = ceil(G/5) for 5 kg bags; pounds = G×2.20462.
Frequently asked questions
Why does a smaller tile size increase the grout needed so much?
Grout scales with joint length, not floor area. The calculator derives tiles per square foot from tile length and width, then multiplies by (length plus width) per tile, so a 4-inch tile creates roughly three times the joint length of a 12-inch tile over the same area. With a 0.125-inch joint and 0.375-inch thickness it applies a 1.6 gram per cubic centimetre density, so a 100 square foot mosaic needs about 9 kilograms versus roughly 3 kilograms for large format.