Grout Calculator UK
Calculate the grout-joint volume from your actual tiled area, tile size, joint width and joint depth. Convert litres into kg and whole packs only when you have the real density and pack size for the grout you intend to use.
Calculate grout quantity
Use the finished tile and joint dimensions you are actually installing. The calculator makes no assumption about grout density, pack size or extra material.
How this grout calculator works
With all tile and joint dimensions entered in millimetres, the numeric result is litres of joint volume per square metre. Multiply by tiled area for the base grout volume.
Mass is deliberately optional
Litres only become kilograms when the density of the actual grout product is known. This calculator does not hard-code a generic cementitious-grout density.
Why tile and joint dimensions matter
Small tiles create more joint length per square metre than large tiles. Wider or deeper joints also increase the volume that must be filled. That is why a single “kg of grout per m²” figure cannot be universal.
Use the floor or wall area whose tile joints will actually be filled.
Use the real tile length/width plus the specified joint width and the depth being grouted.
Use the manufacturer’s density and the supplier’s pack size if you want kg and whole-pack results.
Why there is no 10% default
Mapei’s current UK grout calculator says its result is indicative because tile roughness, residual material and surface irregularities can still affect actual consumption. Those factors vary by job, so this tool starts at 0% and leaves any additional planning quantity visible and under your control.
Worked geometry example
For 20 m² of 600 × 300 mm tiles with 3 mm-wide joints filled to 9 mm depth, the geometric joint volume is about 0.135 L/m², or 2.70 litres before any extra allowance. The calculator stops at volume unless you enter product density; it does not invent a kg conversion.
Grout quantity vs tiles and adhesive
This page owns grout joint volume and optional product-mass/pack conversion. Use the Tile Calculator for tile and box count and the Tile Adhesive Calculator for adhesive bags. Keeping those jobs separate prevents one set of assumptions from contaminating another.
Planning estimate only. The geometric result does not choose a grout, confirm joint suitability or replace the product technical data. Verify the grout is suitable for the tile, joint width, location and installation, and follow the current manufacturer instructions.
Current manufacturer cross-check
- Mapei UK grout calculator — uses tile length, tile width, tile thickness, grout-joint width and grouted area, then calculates consumption from joint volume and product density.
- Mapei Ultracolor Plus — product page includes the same dimension-led consumption calculator and demonstrates that the selected grout product matters.
Frequently asked questions
How much grout do I need per m²?
There is no single trustworthy kg-per-m² figure for every job. Tile size, joint width, joint depth and product density all affect consumption. Enter the actual geometry above.
Is tile thickness the same as grout depth?
Manufacturer calculators commonly ask for tile thickness because it is part of the joint-volume calculation. On site, use the depth that your specified system actually fills with grout rather than assuming every installation is identical.
Why does the calculator ask for density?
Geometry gives a volume in litres. Converting that volume to kilograms requires the density of the grout product. Leaving density blank gives a valid volume estimate without inventing a material property.
How many bags of grout should I buy?
Enter the actual product density and pack size. The calculator converts the planned mass and rounds up to whole packs. If either value is unknown, check the current product technical data or supplier information first.