Grout Calculator
Grout calculator works out Bags to buy and Grout needed from Tiled area, Area unit and Tile length. The default figures on this page give bags to buy of 1; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
5 steps
- Grout per unit area = ((L + W) / (L x W)) x joint width x joint depth = 198.438 cm3 per m2 of tiling.
- Over 9.29 m2 that is 1.844 litres of grout.
- At 1577.2 kg/m3 that weighs 2.91 kg (6.41 lb).
- One 25 lb bag covers about 390 sq ft.
- Bags needed = 0.26, rounded up to 1.
Figures from manufacturer grout coverage tables. Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed · how reference data is kept current
Sources and references
2 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the grout calculator calculates
Works out how much tile grout a job needs from the tiled area, the tile size, the joint width and the joint depth: the volume of grout, its weight at your product’s density, the number of bags and the coverage one bag gives.
How to use this grout calculator
Enter Tiled area, Area unit, Tile length and Tile width. Bags to buy updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Bags to buy, Grout needed and Grout volume.
The method follows Grout joint geometry (derivation) and MAPEI, Ultracolor Plus FA technical data sheet - Approximate Coverage table.
MAPEI's published row: 12in x 12in x 3/8in tile, 1/8in joint, 10 lb bag example
With Tiled area: 156, Area unit: ft2, Tile length: 12, Tile width: 12, the calculator returns Coverage per bag: 156, Bags to buy: 1. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Bags to buy, Grout needed and Grout volume. The inputs you can vary are Tiled area, Area unit, Tile length, Tile width, Grout joint width and Grout joint depth (tile thickness).
Understanding Bags to buy, Grout needed and Grout volume
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.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I calculate how much grout I will need?
Works out how much tile grout a job needs from the tiled area, the tile size, the joint width and the joint depth: the volume of grout, its weight at your product’s density. Open “How this is worked out” beside the result to see each step for your own figures.
How much grout is needed for 50 sq ft?
On the figures this page opens with — tiled area 156, tile length 12, tile width 12 and grout joint width 0.125 — the bags to buy is 1. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
What information do I need for the grout calculator?
You need Tiled area, Area unit, Tile length, Tile width, Grout joint width, Grout joint depth (tile thickness), Tile and joint unit and Grout density (from the product data sheet). The page opens with default figures that give bags to buy of 1, so you can see the scale before entering your own.
What does this grout calculator show?
It shows Bags to buy, Grout needed, Grout volume, Coverage per bag, Grout per unit of tiled area, Grout volume, exact grid geometry, Share of the surface that is joint and Bags needed before rounding up, with the working and any warnings for your entries.
Can I check how the grout calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.