Grout Calculator
Estimate grout and whole bags from tile joints and your product's consumption coefficient.
This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.
Estimate grout weight and whole packages for rectangular tiles using joint dimensions and a product-specific manufacturer consumption coefficient, with a transparent allowance.
How to use it
- 1Choose metric or US units and enter the tiled area, tile sides and specified filled joint dimensions.
- 2Enter K from the matching manufacturer coverage formula, purchased package weight and your allowance.
- 3Review kg/m², required weight, whole packages, surplus and formula limitations.
- 4Download a JSON estimate; changing any field clears stale output.
Example
- Input
- 10 m², 300 × 300 mm tiles, 3 mm joints, 10 mm depth, K 1.5, 10% allowance, 2 kg/package.
- Output
- 0.3 kg/m²; 3.3 kg required; 2 packages = 4 kg, with 0.7 kg package surplus.
Approximate product-specific formula; K is not a universal grout density.
What happens to your data
Dimensions and product settings are calculated locally and are not uploaded or saved. The optional JSON download includes those inputs and assumptions.
Last updated October 2026
Grout use changes with tile size, joint width, filled depth and the product itself. This grout calculator estimates consumption for uniform rectangular tiles using a manufacturer-style formula and a coefficient you supply from the actual product documentation. It does not assume that every cementitious, epoxy or ready-mixed grout has the same density or coverage.
The result shows kg/m², required product weight before and after your allowance, whole packages and the surplus caused by package rounding. Metric and US customary inputs are available, and an optional JSON estimate records dimensions, units, coefficient and assumptions. Use the estimate as a purchasing check alongside the current manufacturer's coverage and application instructions.
How it works
For tile sides A and B, filled joint depth C and joint width D, all in millimetres, the calculation is (A+B)/(A×B) × C × D × K = kg/m². This approximate method is published in MAPEI product documentation. Multiplying the resulting rate by the tiled area in m² gives base product mass. Your selected allowance is applied before the result is divided by purchased product mass per package and rounded up.
K is the consumption coefficient for that specific formula, not a generic field for loose powder density, mixed mortar density or mixing-water proportion. A product sheet can list more than one density value; substituting the wrong one changes the order. For example, the cited Keracolor FF sheet uses K = 1.5 in its consumption formula. The calculator starts with K empty because that example is not a recommendation for your product, region or installation. If your product uses a different coverage method, use its own calculator rather than forcing it into this one.
The formula is an approximation for a repeating tiled surface, not an exact joint intersection and perimeter simulation. It does not compute irregular mosaics, different tile groups, adhesive beds, movement-joint sealant or textured-surface losses. This version requires each tile side to be at least five times joint width as a software scope boundary; that is not an installation standard. Filled depth must follow the actual product instructions. Where a sheet specifies tile thickness, do not enter a shallower depth merely to lower the quantity.
US mode converts ft² to m² and inches to millimetres before applying the same metric formula; K remains the manufacturer's coefficient for kg/m². Required weight and package size are then expressed in pounds. Purchased weight must use the same product-mass basis as the consumption formula, not powder plus added water. Exact decimal fractions are used for conversion and package decisions before display rounding. Physical consumption is still uncertain even when the arithmetic is exact.
Worked example: Whole packages after a stated allowance
- Input
- 10 m²; 300 × 300 mm tiles; 3 mm joints; 10 mm fill depth; product K = 1.5; 10% allowance; 2 kg packages.
- Result
- 0.3 kg/m²; 3 kg before allowance; 3.3 kg required; 2 packages = 4 kg; 0.7 kg from package rounding.
Coefficient and allowance are example inputs. Check the actual product's current coverage formula and required fill depth.
Common use cases
- Estimate grout for one uniform rectangular-tile floor or wall using the actual product's consumption coefficient.
- Compare how joint width or specified fill depth changes product weight without hiding those assumptions.
- Check whether a measured area fits one package or requires another, while separating allowance from package surplus.
- Download a detailed JSON estimate to retain measurements and product assumptions for a supplier discussion.
Frequently asked questions
Where do I find coefficient K?＋
Look for the consumption formula in your grout's current technical data sheet, with output kg/m² and dimensions in mm. Use its coefficient only if the formula matches (A+B)/(A×B) × depth × width × K. Do not substitute a separate powder or mixed-density figure. If no matching coefficient is provided, use the manufacturer's coverage table or calculator.
Does the example prove every grout needs 0.3 kg/m²?＋
No. With 300 × 300 mm tiles, 10 mm filled depth, 3 mm joints and K = 1.5, this formula produces 0.3 kg/m². Every variable matters. It is a checked arithmetic example, not a claim about other products or site conditions.
Should I enter tile thickness or joint depth?＋
Enter the specified filled depth used by the product's coverage method. Some sheets use full tile thickness. Follow the manufacturer's requirements for preparation and fill; this tool does not recommend a minimum depth or permit reducing it to save material.
Can I estimate epoxy grout or multi-part kits?＋
Only when the product explicitly supports the same formula and coefficient. Enter the purchased product mass corresponding to that formula. Use complete kit quantities and manufacturer component ratios; this calculator cannot validate chemistry, mix ratios or partial-kit use.
Why can an actual job use more grout?＋
The model does not inspect surface texture, irregular gaps, residual adhesive, cleaning loss or installation technique. The allowance is your own estimate and starts at zero. Manufacturer guidance and a trial area are more informative than treating a displayed decimal as a guaranteed yield.
What limits does the calculator apply?＋
It accepts positive plain decimals with up to six decimal places, an area up to 100,000 m², tile sides of 10–3,000 mm, joint width up to 30 mm, filled depth up to 100 mm, K from 0.1 to 5 and package mass up to 1,000 kg. Tile sides must be at least five times joint width. These are calculation limits, not product suitability claims. Changing units clears all measurements and product settings.
Is my project information stored?＋
Calculation happens locally; measurements are not uploaded or saved by the tool. An optional JSON file includes the inputs and formula assumptions on your device. Changing any field invalidates the previous result and download.
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