Grout Calculator
Enter the area and your tile and joint sizes. The grout calculator works out the volume of the joints, turns it into kg or lb with the density of your grout, and rounds up to whole bags. If your bag prints a coverage chart, switch to the bag’s figure instead.
Grout calculator
Quantities are estimates. Buy from one batch and keep a few spare pieces for repairs. Mix and coverage differ by product; the bag’s data sheet wins.
In m²; 168 sq ft works too.
Bare numbers are mm.
Bare numbers are mm.
Bare numbers are mm.
Usually the tile thickness. Bare numbers are mm.
Typical value. Check your product’s data sheet or box label.
Your price, any currency. Leave blank to skip.
Assumptions
Change any value to match your product or local rules.
Basis: Example. Your grout’s data sheet gives its density or a kg per m² figure; epoxy grouts differ.
Basis: Example allowance for cuts and breakage. Your installer’s figure wins; the Tile Layout Planner counts the cuts for one room.
- Grout per area
- 0.143 kg/m² (2.93 lb per 100 sq ft)
- Joint volume
- 1.35 L
- Grout needed (with wastage)
- 2.4 kg
- 5.2 lb
- Bags
- 1
- Left over
- 2.6 kg
- Cost (your currency)
- Add a price to see the cost
2.4 kg of grout fills the joints of 15.12 m² with 10.0% added: 1 bag of 5.0 kg.
How this was calculated
- Joint volume per m² = joint × (tile length + tile width + joint) × depth ÷ ((tile length + joint) × (tile width + joint))
- Grout = joint volume × density × area × (1 + wastage); bags = grout ÷ bag size, rounded up
- From the bag: bags = area × (1 + wastage) ÷ area one bag covers, rounded up
- Joint volume per m² = 3 mm × (600 mm + 600 mm + 3 mm) × 9 mm ÷ ((600 mm + 3 mm) × (600 mm + 3 mm)) = 0.0893 L/m²
- Grout per m² = 0.0893 L/m² × 1.60 kg/L = 0.143 kg/m²
- Grout needed = 0.143 kg/m² × 15.12 m² × (1 + 10.0%) = 2.4 kg
- Bags = 2.4 kg ÷ 5.0 kg, rounded up = 1
How it works
Enter the area
The floor or wall area you will tile, in m² or sq ft.
Enter the tile and joint
Tile length and width, joint width and joint depth. Bare numbers are mm in metric and inches in imperial.
Check the density
The 1.6 kg/L in the assumptions is an example. Your grout’s data sheet gives its own figure.
Read the bags
Grout needed with your wastage allowance, rounded up to whole bags of the size you buy.
Worked example
A 15.12 m² floor of 600 × 600 mm tiles with 3 mm joints, 9 mm deep. Each m² holds 3 × (600 + 600 + 3) × 9 ÷ (603 × 603) = 0.0893 L of joint. At 1.6 kg/L that is 0.143 kg/m², so 2.16 kg for the floor and 2.38 kg with 10% added: one 5 kg bag.
In feet: 168 sq ft of 12 × 12 in tiles with 1/8 in joints, 3/8 in deep, takes 11.8 lb with 10% added. That is two 10 lb bags.
Where the grout goes
Grout fills the joints, so the sum is the joint volume: each tile brings one joint along its length and one along its width, as deep as the joint. Smaller tiles mean more joint per m², and a mosaic floor takes many times the grout of a large-format floor with the same joint width.
The formula counts a large straight grid. Edges, cuts and a brick or herringbone pattern change it a little; the wastage allowance covers that and what stays in the bucket.
Joint width and depth
Grout use grows in step with both. A 6 mm joint takes about twice the grout of a 3 mm joint, and the depth is usually the tile thickness, less anything left in the joint from the adhesive. Your tile and your installer decide the joint width. Measure a tile’s thickness for the depth if you are unsure.
Using the bag’s coverage chart instead
Many bags print the area one bag covers for a few tile sizes and joint widths. Choose “From the coverage on the bag”, type the area for your tile and joint, and the calculator divides your area with wastage by it. The bag’s figure comes from the maker’s own tests, so it wins over the joint formula when the two differ.
Epoxy and cement grouts
Cement grouts and epoxy grouts have different densities, and epoxy is often sold in kits by weight or volume. Change the density to the figure on your data sheet. If the sheet gives kg per m² for your joint, multiply by your area and compare it with the result here.
Frequently asked questions
How much grout do I need per m² or sq ft?
It depends on the tile size, joint width and joint depth. For 600 × 600 mm tiles with a 3 mm joint, 9 mm deep, and a grout of 1.6 kg/L, the calculator gives 0.143 kg/m² (2.93 lb per 100 sq ft). Smaller tiles or wider joints need more.
How do I calculate grout for large tiles?
The same way: joint volume per m² = joint × (length + width + joint) × depth ÷ ((length + joint) × (width + joint)). Large tiles have fewer joints per m², so they take less grout for the same joint width.
Does joint depth matter?
Yes. Grout use is in proportion to the depth, so a 12 mm deep joint takes a third more than a 9 mm one. Use the tile thickness unless your installer leaves the joint shallower.
How much epoxy grout do I need?
Work out the joint volume here and enter the density from the epoxy’s data sheet. If the kit states the area it covers for your joint, use the bag coverage method with that figure.
How many bags of grout for a bathroom?
Enter the floor and wall areas together, or work them out one at a time if the tiles differ. A 5 m² floor of 300 × 300 mm tiles with 3 mm joints, 9 mm deep, at 1.6 kg/L takes about 1.6 kg with 10% added: one 5 kg bag.
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