Grout Calculator
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- Imperial and metric
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7.2 lb of grout: 1 × 10 lb bag
This is an estimate. The coverage chart on the grout bag is the final word, and unsanded and epoxy products can differ from cement sanded grout.
How to use the grout calculator
- Enter the tiled area as length × width, or switch to Total area if you already know it. To count tiles, grout and thinset together, use the tile calculator.
- Enter the tile length, width and thickness. Thickness matters because grout fills the joint to roughly the full depth of the tile.
- Enter the joint width. In inches, type fractions as decimals: 1/16 = 0.0625, 1/8 = 0.125, 3/16 = 0.1875, 1/4 = 0.25.
- Choose the grout type and bag size. Leave the density at the typical value unless you have a better figure, and keep about 10% extra for mixing and clean-up.
Grout formula
Each tile has one joint along its length and one along its width, so the length of joint per unit of area is (L + W) ÷ (L × W). Multiply that by the joint width and depth to get the volume to fill, then by the weight of powder it takes to fill that volume.
Grout (lb) = Joint volume × 100 lb/ft³ × (1 + waste %)
L and W are the tile length and width, J is the joint width and T is the tile thickness, all in inches. In metric the same formula is often written as kg per m² = (L + W) ÷ (L × W) × T × J × 1.6, with all four sizes in millimeters.
The 100 lb/ft³ (about 1.6 kg per liter) is a typical figure for cement grout powder, so the result is an estimate. The coverage chart on the grout bag is the final word, and unsanded and epoxy products can differ. If your bag's chart gives a different coverage for your tile, adjust the density until the calculator matches it, and the other results will follow.
Worked example: subway tile shower walls
Three shower walls add up to 80 ft² of 3 × 6 inch subway tile, 5/16 inch thick, with 1/16-inch joints. The joints hold 0.065 ft³, which takes about 6.5 lb of grout powder, or 7.2 lb with 10% extra. That is one 10 lb bag, and joints this narrow usually call for unsanded grout. The same area of 12 × 24 inch tile, 3/8 inch thick with 1/8-inch joints, needs only about 4.3 lb, because large tiles have far fewer joints.
Grout per 100 square feet
Pounds of cement grout at 100 lb/ft³, including 10% extra, for the tile thickness shown.
| Tile (L × W × thickness) | 1/16 in joint | 1/8 in joint | 3/16 in joint | 1/4 in joint |
|---|---|---|---|---|
| 2 × 2 × 1/4 in | 14.3 lb | 28.6 lb | 43 lb | 57.3 lb |
| 3 × 6 × 5/16 in | 9 lb | 17.9 lb | 26.9 lb | 35.8 lb |
| 6 × 6 × 3/8 in | 7.2 lb | 14.3 lb | 21.5 lb | 28.6 lb |
| 12 × 12 × 3/8 in | 3.6 lb | 7.2 lb | 10.7 lb | 14.3 lb |
| 6 × 24 × 3/8 in | 4.5 lb | 9 lb | 13.4 lb | 17.9 lb |
| 12 × 24 × 3/8 in | 2.7 lb | 5.4 lb | 8.1 lb | 10.7 lb |
| 24 × 24 × 3/8 in | 1.8 lb | 3.6 lb | 5.4 lb | 7.2 lb |
To see how far a bag goes, divide its weight by the figure and multiply by 100. For 12 × 12 inch tile with 1/8-inch joints, a 25 lb bag covers about 25 ÷ 7.2 × 100 ≈ 349 ft².
Metric: grout in kg per m²
At 1.6 kg/L, including 10% extra.
| Tile (L × W × thickness) | 2 mm joint | 3 mm joint | 5 mm joint |
|---|---|---|---|
| 100 × 100 × 6 mm | 0.42 kg | 0.63 kg | 1.06 kg |
| 75 × 150 × 7 mm | 0.49 kg | 0.74 kg | 1.23 kg |
| 200 × 200 × 8 mm | 0.28 kg | 0.42 kg | 0.7 kg |
| 300 × 300 × 9 mm | 0.21 kg | 0.32 kg | 0.53 kg |
| 300 × 600 × 9 mm | 0.16 kg | 0.24 kg | 0.4 kg |
| 600 × 600 × 10 mm | 0.12 kg | 0.18 kg | 0.29 kg |
Sanded, unsanded or epoxy?
- Sanded grout is typically used for joints about 1/8 inch (3 mm) and wider. The sand helps wider joints resist shrinking and cracking.
- Unsanded grout is typically used for joints narrower than about 1/8 inch, and it is often chosen for polished stone, glass and other surfaces that sand could scratch.
- Epoxy grout resists stains and chemicals better than cement grout, but it costs more and has a short working time. It is sold in kits, and its yield is not the same as cement grout, so use the kit's coverage chart for the final quantity.
Some newer grouts are rated for a wide range of joint widths, so check the joint range on the bag before you buy.
Tips for grouting
- Clean the joints first. Remove spacers and any thinset that squeezed up, so the grout can fill the joint to full depth.
- Mix in small batches. Mix only what you can use within the working time printed on the bag.
- Buy it all at once. Grout color can vary slightly between batches, so buy enough for the whole job from one batch.
- Wide joints add up. Grout use grows in direct proportion to joint width and tile thickness: doubling the joint width doubles the grout.
- Sealing. Cement grouts are often sealed once cured. Follow the grout maker's advice on whether and when to seal.
Frequently asked questions
How much grout do I need for 100 square feet?
It depends mostly on the tile size and joint width. For 12 × 12 inch tiles 3/8 inch thick with 1/8-inch joints, this calculator estimates about 7.2 lb including 10% extra. The same area of 12 × 24 inch tile needs about 5.4 lb, while 2 × 2 inch mosaic tile 1/4 inch thick needs about 29 lb, because small tiles have far more joint per square foot.
How many square feet does a 25 lb bag of grout cover?
With 12 × 12 × 3/8 inch tiles and 1/8-inch joints, a 25 lb bag covers roughly 350 sq ft by this estimate, including 10% extra. With 1/4-inch joints it covers about 175 sq ft, and small tiles cover much less. The coverage chart printed on the bag is the figure to trust for your product.
Should I use sanded or unsanded grout?
As a general guide, sanded grout is used for joints about 1/8 inch (3 mm) and wider, and unsanded grout for narrower joints. Unsanded grout is also often chosen for polished stone, glass and other surfaces that sand could scratch. Joint ranges vary between products, so check the bag.
How do I calculate grout in kg per square meter?
Use kg/m² = (L + W) ÷ (L × W) × T × J × 1.6, with the tile length L, width W, thickness T and joint width J all in millimeters. For 300 × 300 mm tiles 9 mm thick with 3 mm joints, that is about 0.29 kg/m², or 0.32 kg/m² with 10% extra, so a 5 kg bag covers roughly 16 m². The 1.6 is a typical figure, and your product may differ.
Can I use this calculator for epoxy grout?
Yes, as a first estimate. Epoxy grout is sold in kits by weight and its yield is not the same as cement grout, so use the coverage chart that comes with the kit for the final quantity. If the chart gives a different figure for your tile, adjust the density field until the calculator matches it.