Grout Calculator
Buy the right amount of grout the first time. Enter your tiled area, tile size, joint width and joint depth, and this grout calculator works out how many pounds of grout you need and how many 10 lb or 25 lb bags to buy, with a waste allowance.
Your results will appear here.
How to use the grout calculator
- Enter the tiled area in square feet. For a floor, multiply length by width. For a wall, multiply width by tiled height.
- Enter the tile length and width. Use the actual tile size in inches, such as 12 x 24.
- Enter the joint width. This is the spacer size, such as 1/16 in, 1/8 in or 3/16 in. You can type fractions like 1/8.
- Enter the joint depth. For most installs this equals the tile thickness, such as 3/8 in for porcelain floor tile.
- Choose a waste allowance and bag size. 10% covers mixing loss and cleanup for most projects.
How much grout you need: the formula
Grout fills the joints around each tile. For every tile, the joint area is the space between the tile and the next one on two sides. The calculator works out the joint volume for each square foot of floor, then converts it to weight:
Volume per sq ft (cu in) = 144 × J × (L + W + J) ÷ ((L + J) × (W + J)) × D
Pounds = Area × Volume per sq ft × 0.068
Where L and W are the tile length and width, J is the joint width and D is the joint depth, all in inches. The figure 0.068 lb per cubic inch is a typical density for cement-based grout.
Worked example
100 sq ft of 12 x 12 in tile with 1/8 in joints and 3/8 in depth:
- Volume per sq ft = 144 × 0.125 × 24.125 ÷ (12.125 × 12.125) × 0.375 = about 1.11 cu in
- Grout = 100 × 1.11 × 0.068 = about 7.5 lb
- With 10% waste: about 8.3 lb, so one 10 lb bag (or one 25 lb bag)
Grout coverage chart
Pounds of grout for 100 sq ft without waste, calculated with the formula above:
| Tile size | Joint width | Joint depth | Grout per 100 sq ft |
|---|---|---|---|
| 2 x 2 in mosaic | 1/16 in | 1/4 in | 14.6 lb |
| 4 x 4 in | 1/8 in | 1/4 in | 14.6 lb |
| 3 x 6 in subway | 1/8 in | 5/16 in | 18.2 lb |
| 6 x 6 in | 1/8 in | 5/16 in | 12.4 lb |
| 12 x 12 in | 1/8 in | 3/8 in | 7.5 lb |
| 12 x 24 in | 1/8 in | 3/8 in | 5.7 lb |
| 18 x 18 in | 3/16 in | 3/8 in | 7.5 lb |
| 24 x 24 in | 1/8 in | 3/8 in | 3.8 lb |
Small tiles have many more joints per square foot, which is why mosaics and subway tile use far more grout than large-format tile.
Sanded or unsanded grout?
- Unsanded grout is smooth and sticky, made for narrow joints of 1/8 in or less. It is often used on wall tile and with polished stone that sand could scratch.
- Sanded grout contains fine sand that keeps wider joints from shrinking and cracking. It is the usual choice for joints wider than 1/8 in.
- Epoxy grout resists stains and water very well, which makes it popular in showers and kitchens. It costs more and is harder to work with.
Tips for grouting
- Check your grout’s coverage chart. Brands differ, and the bag may show a slightly different number from this calculator.
- Mix only what you can use in about 30 minutes.
- Buy a little extra from the same batch so any later repairs match in color.
Frequently asked questions
How much grout do I need for 100 sq ft?
It depends mostly on tile size and joint width. For 12 x 12 in tile with 1/8 in joints and 3/8 in depth, you need about 7.5 lb for 100 sq ft, or about 8.3 lb with 10% waste. Small mosaic or subway tile can need 15 to 20 lb.
How many square feet does a 25 lb bag of grout cover?
With 12 x 12 in tile and 1/8 in joints, a 25 lb bag covers about 330 sq ft. With 3 x 6 in subway tile and 1/8 in joints, the same bag covers only about 135 sq ft. Enter your own tile size above for an exact figure.
What grout joint width should I use?
Rectified porcelain tile is often set with 1/16 to 1/8 in joints, while handmade or uneven tile needs wider joints. Follow the tile manufacturer's recommendation for the minimum joint width.
Is joint depth the same as tile thickness?
Usually yes. Grout should fill the joint almost to the top of the tile, so the depth is close to the tile thickness minus any thinset that squeezes into the joint.
Does this work for wall tile?
Yes. Enter the wall area in square feet and your tile and joint sizes. The calculation is the same for floors and walls.
Sources and methodology
The formulas on this page were written and checked by the HomeQuantly Team against the worked examples shown above. Results are estimates for planning; always confirm measurements on site before you buy materials.