How much grout do you need for your tiles? Estimate the grout mass, whole packs and optional material cost. Use tile and joint dimensions with a product-specific factor, or enter matching coverage data from your grout manufacturer.
How to use the grout calculator
- Enter the installed tiled area in square feet or square metres. Include ordinary grout lines in that area.
- Choose your calculation method. For the dimension method, enter the actual tile length and width, joint width, filled depth and the product consumption factor.
- If your manufacturer already gives a matching consumption rate or coverage per pack, enter that instead of estimating from geometry.
- Set an additional allowance, the net mass of one pack and any usable matching grout you already have.
- Optionally add the price per pack, then select Calculate grout. The result rounds the remaining need up to whole packs.
Use decimal numbers with a point or comma, without fractions or thousands separators. For a 1/8 inch joint, enter 0.125 in. The calculator converts dimension inputs to millimetres internally. Changing length, area or mass units converts the related values already entered. A manufacturer rate converts with both area and mass units. Recalculate after editing an input.
How is grout consumption calculated?
For regular rectangular tiles, the dimension mode uses this approximate formula:
Consumption in kg/m² = ((A + B) ÷ (A × B)) × J × D × K.
- A is the actual tile length in millimetres.
- B is the actual tile width in millimetres.
- J is the joint width in millimetres.
- D is the depth filled with grout in millimetres.
- K is the product's consumption factor for this formula.
This estimates the amount of purchased grout for each square metre. It is an approximation for a repeating rectangular layout, not an exact volume model for every edge shape. The result is converted to your selected units.
Where do I find the product factor K?
Look for a consumption formula or grout coverage figure in the product's technical sheet. Check that it uses millimetres for tile and joint dimensions and returns kg/m². Do not copy a number from an unrelated density table.
For example, the ARDEX-FLEX FS technical sheet specifies a coverage factor of 1.5 for this formula. The same sheet lists different values for powder bulk density and fresh mortar density. They are different inputs. This is why the factor field starts empty. If your product has no compatible factor, use its matching consumption rate or coverage per pack.
How do packs and allowance work?
- Base grout mass = tiled area × base consumption.
- Estimated need = base mass × (1 + additional allowance ÷ 100).
- Shortfall = estimated need − usable existing stock, with a minimum of zero.
- New packs = shortfall ÷ net mass per pack, rounded up.
- New purchased mass = new packs × net mass per pack.
In manufacturer-rate mode, the entered mass per area is the base consumption. In coverage mode, base consumption is the net mass of the entered pack divided by its stated coverage. Use figures for exactly the same product, pack size, tile and joints. If a source already includes wastage, only add any further allowance you intend.
Example: grout for 20 square metres
Assume rectangular tiles of 300 × 600 mm, joints 3 mm wide and a filled depth of 8 mm. Use K = 1.5 for this example, a 10% additional allowance, 2.5 kg packs and no existing stock.
- Base consumption: (300 + 600) ÷ (300 × 600) × 3 × 8 × 1.5 = 0.18 kg/m².
- Base mass: 20 × 0.18 = 3.6 kg.
- With the chosen allowance: 3.6 × 1.10 = 3.96 kg.
- Whole packs: round 3.96 ÷ 2.5 up to 2 packs.
- New purchased mass: 2 × 2.5 = 5 kg.
At an example price of EUR 25 per pack, the new grout costs EUR 50. This is an illustrative price, not a current offer. Load example fills these values. If you already had 1.5 kg of usable matching grout, the shortfall would be 2.46 kg and one 2.5 kg pack would cover this estimate.
What area should I enter?
Use the surface actually being grouted. For a rectangular floor, multiply its length by width. Add separate wall and floor areas only if they use the same tile dimensions, joint details and grout. Remove genuinely untiled openings, without counting overlapping sections twice.
Do not use the larger area of tile packs you bought with cutting or repair stock. Tiles left in a box do not create installed grout joints. Do not subtract the ordinary grout lines from the tiled area either. If you need help with the tile purchase, use the tile calculator.
Which joint depth should I use?
Use the depth that will actually be filled according to your installation instructions. Tile thickness may help identify the joint depth, but adhesive left in the joint, a shaped edge or a recessed finish can change the space being filled. Do not enter the tile plus the full adhesive-bed thickness.
Check the prepared joints and the grout manufacturer's minimum filling requirements. Do not deliberately leave a shallow joint to make a smaller calculated quantity fit. The calculator measures no joints and does not decide whether the installation is prepared correctly.
Is a 10% allowance always enough?
No. Ten percent is a starting input you can change. Tile texture, edge shape, how much material remains on tools, cleaning losses and the size of each working batch can change actual consumption. A small job can lose a larger share of its grout during handling than a broad, regular surface.
For an unfamiliar tile or grout, use the manufacturer's coverage guidance or a measured trial. A rough surface, deeply bevelled edges, very wide joints or irregular mosaic pieces deserve particular attention. The tool flags joints wider than one tenth of the shorter tile dimension as a reason to verify coverage. That threshold is an estimating prompt, not a product approval limit.
Can I use this for mosaics, epoxy grout or premixed grout?
For rectangular mosaic pieces, use the individual piece size, not the size of the mesh sheet, and verify the result against the product coverage. Pebbles, hexagons and irregular pieces do not match the rectangular formula. Use a matching manufacturer rate or a trial for those shapes.
For epoxy or premixed products, use their own coverage data. Do not assume a cement-grout factor applies. With a multi-component kit, use the manufacturer's net kit mass and coverage on the same basis. With a product sold by volume, use its published mass equivalent and matching coverage; do not assume one litre equals one kilogram.
What about existing grout, different colours and movement joints?
Only deduct stock that is still usable and matches the intended product and colour. Hardened leftovers cannot be treated as available material. Check storage condition and shelf life. Consider a colour check when combining batches.
Run separate calculations for different grout products or colours. If the same product and colour are used across different tile sizes, calculate each base mass, add those masses and apply your project allowance before rounding a combined order. Adding separately rounded pack counts can overstate the total. The calculator itself handles one tile/joint specification at a time.
Movement joints, perimeter joints and changes of plane need the joint treatment specified for the installation. This calculator does not design those details or estimate flexible sealant. It also does not calculate adhesive, waterproofing, mixing water, installation time or product suitability.
Check the product before ordering
Use the current ARDEX-FLEX FS product page and coverage calculator and its technical sheet as examples of where to find product-specific data. Your own grout's instructions and coverage take precedence. The photo illustrates a grouting project and does not define a recommended product or joint size.
For other room materials, try the flooring and underlay calculator or the paint calculator.
