Thinset & Grout Calculator
Work out how many bags of thinset and how many packs of grout your tile job needs, based on tile size, joint width and the trowel you will use
Tile Job Details
Use the weight printed on the products you plan to buy so the count matches your shopping list
Large tile (over 900 cm² / 140 in²) needs full thinset contact: switch to back-buttering or double coating.
Estimate based on typical consumption. Always check the coverage printed on your product's data sheet and buy one spare bag.
How to use this tool
- Choose Metric or US units and enter the area to tile and the waste allowance.
- Enter the tile length, width and thickness, and the grout joint width.
- Select the trowel notch depth and the application method (single coat, back-buttering or double coat).
- Enter your thinset bag size and grout pack size, then read the bags and packs to buy.
Worked example
For a 200 ft² floor of 24 × 24 in tiles, 3/8 in thick with a 1/8 in joint, a 10 mm notch trowel and back-buttering, thinset use is 0.5 kg/m² per mm of notch × 10 mm × 1.25 for back-buttering, which is 1.28 lb/ft². With 10% waste that is 200 × 1.28 × 1.10 = 281.6 lb, so 6 bags of 50 lb. Grout runs at only 0.03 lb/ft², or 7.2 lb with waste: 2 packs of 5 lb. Large tiles of this size should be back-buttered so the whole back makes contact. Coverage per bag varies by product, so check the data sheet before buying.
Methodology
Two separate calculations run side by side: grout is a volume problem (how much joint has to be filled), while thinset is a trowel problem (how much adhesive the notch leaves on the surface). Both results are increased by your waste allowance and rounded up to whole bags.
Where thinset and grout quantities get lost
Unless stated otherwise, the numbers below use 20 m², 60 × 60 cm tiles that are 10 mm thick, a 3 mm joint, a 10 mm notch (5 kg/m²), back-buttering and 10% waste.
- Using one grout figure for every tile. Grout use depends on tile size. With these 60 × 60 cm tiles the tool gives 0.16 kg/m², about 3.5 kg in total. Switch to 10 × 10 cm tiles that are 8 mm thick and it jumps to 0.77 kg/m², or 16.9 kg.
- Widening the joint without re-counting. Grout use grows in proportion to joint width. Going from 3 mm to 5 mm turns 3.5 kg into 5.9 kg, which is 4 and 6 packs of 1 kg.
- Picking a bigger notch to be safe. Thinset rises with notch depth. A 6 mm trowel with single coat means 66 kg (4 bags of 20 kg); a 12 mm one means 132 kg (7 bags). Use the notch your tile and adhesive data sheet call for.
- Skipping back-buttering on large tiles to save adhesive. Single coat is 110 kg (6 bags), back-buttering is 137.5 kg (7 bags) and double coat is 220 kg (11 bags). A 60 × 60 cm tile is 3,600 cm², well over the 900 cm² level where the tool shows its warning.
- Leaving the bag sizes at the defaults. The same 137.5 kg is 7 bags of 20 kg but 6 bags of 25 kg, and 3.5 kg of grout is 4 packs of 1 kg or 1 pack of 5 kg. Enter the weights printed on the products you will buy.
These are planning estimates based on typical consumption; always check the data sheets.
Tools for Setting Tile and Grouting
Trowels, leveling clips and grout floats that pair with the quantities above
DIXIANG Stainless Steel Notched Trowel Set with Rubber Grout Float and Sponge
Square-notch stainless steel trowels plus a rubber grout float and grout sponge, covering spreading, grouting and cleanup in one purchase.
DGSL Tile Leveling System with Pliers, 300 Spacers (1/8 in) and 100 Wedges
Clip-and-wedge leveling system with pliers that keeps tile edges flush (anti-lippage) while the thinset cures.
QEP Molded Rubber Grout Float, 4 × 9.5 in, Non-Stick Gum Rubber
Non-stick gum rubber float for pressing grout into the joints and scraping off the excess in a single pass.
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Frequently asked questions
Why does tile thickness change how much grout I need? ▼
Grout fills the joint to the full depth of the tile edge, so a 12 mm porcelain slab takes about 20% more than a 10 mm tile with the same joint width. That is why the calculator asks for thickness, not just tile size and joint width.
Why does a bigger trowel notch mean more bags of thinset? ▼
The notch sets the height of the ridges, and the ridges hold the adhesive. Going from a 6 mm to a 10 mm notch raises consumption from roughly 3 to 5 kg/m², so a 20 m² floor needs about 40 kg more before waste. Pick the notch that your tile and thinset data sheets call for, not the biggest one you own.
When do I need back-buttering or a double coat? ▼
As a rule of thumb, once a tile is bigger than roughly 30 × 30 cm (about 12 × 12 in, or 900 cm²), or on floors and exteriors, the tile back should be coated too so no voids remain underneath. Choose back-buttering or double coat above and the calculator raises the thinset rate accordingly. Check the tile and adhesive manufacturers' instructions for your project.
Should I buy exactly the number of bags shown? ▼
The result already includes your waste percentage and is rounded up to full bags. Thinset starts to set in the bucket, so mixing leftovers are normal; one spare bag from the same batch is cheap insurance, while grout color can vary between batches.
Does the grout formula work for epoxy grout and wide joints? ▼
The calculator assumes 1.6 kg per liter of joint, a typical planning value for cement-based grout. Epoxy and other resin grouts have their own densities, so for those use the coverage figure on the product data sheet. For very wide joints (over about 10 mm) or partly filled joints the formula also leaves its comfort zone; treat the result as an estimate and cross-check it with the manufacturer's coverage table.