Grout quantity calculator
Estimate grout in kilograms and whole bags from tile size and joint width; 300 × 300 mm tiles with 3 mm joints leave about 2 % of the area for grout.
- Runs in your browser
- No upload
- Instant result
Quantity estimate only. This does not approve structural safety, load capacity, drainage, fire resistance or building-code compliance. Verify the design and local requirements with a qualified professional. Purchase quantities round up to whole packs.
Assumptions & formula
Formula and assumptions
w = Waste allowance/100; f=1−ab/((a+j)(b+j)); V=Sfd(1+w); kg=V×1000/Y
The prefilled values are editable examples, not product specifications. Enter your supplier’s yield, density, coverage and packaging values, and add an allowance for overlaps, compaction and cuts where needed.
Purchase counts use the exact entered decimals and unit factors, without a rounding tolerance that could discard a real remainder. π and irrational square roots use enclosing bounds; ambiguous counts produce an error. Counts must be safe integers.
Results
Enter values and press Calculate to see the result here.
How to use this calculator
- Set inputs and units
Enter the tiled area, the tile length and width, the joint width and depth, the product yield in L/kg and the bag size in kg.
- Calculate
Check this worked example: area10 m²,tile0.3×0.3 m,joint0.01 m,depth0.01 m,yield0.5 L/kg,pack5 kg,waste0% →jointVolume≈6.34755 L,mass≈12.69511 kg,bags3
- Results
The joint fraction compares the tile area with the area of a tile plus its joint. Don't grout the whole volume of the tiled surface.
Questions and limits
Can kg/L be entered as L/kg?
No. They are reciprocals, so convert the manufacturer’s density or yield before you divide the joint liters by L/kg.
Which input errors should I correct?
Joint width, joint depth and yield must be positive. Convert joints given in millimeters into the geometry unit you selected.
What does this calculation leave out?
A uniform rectangular module estimate. No irregular joints, product compatibility or certification of a waterproofing system.