Grout Calculator
Grout use depends on tile size and joint width more than on area alone. Enter your tile and joint, get pounds and bags.
How it works
The calculator works out the total length of grout joints in your area, multiplies by joint width and tile thickness to get the joint volume, and converts that volume to dry grout weight with a standard allowance for mixing and waste.
- Joint length per unit area = (1 / tile length) + (1 / tile width)
- Joint volume = joint length x gap x tile thickness x area
- Dry grout = volume x approx. 0.06 lb per cubic inch (about 1.7 kg per liter), including waste
Worked example
100 sq ft of 12 in x 12 in tiles, 1/8 in joints, 3/8 in thick tile: the joints total about 200 linear feet. Their volume is roughly 108 cubic inches, which is about 6.5 lb of dry grout - so one 10 lb bag covers it with a little to spare.
Assumptions to know
- This is a planning estimate. Grout density and coverage vary by product, so confirm against the coverage chart on your grout bag.
- A waste and cleanup allowance is included in the conversion factor.
- Epoxy and premixed grouts have different coverage - check the label.
Results are planning estimates only. Always check the coverage and instructions on the actual product you buy, and measure your own space carefully before ordering. When in doubt, a little extra material is cheaper than a second trip or a stalled job.
Frequently asked questions
How much grout do I need for 100 sq ft of tile?
For 12 x 12 tiles with a 1/8 inch joint, roughly 6 to 7 lb of dry grout covers 100 sq ft, so a single 10 lb bag is usually enough. Bigger tiles and narrower joints use less; small tiles and wide joints use much more.
Sanded or unsanded grout?
Unsanded for joints under 1/8 inch and for delicate tile that can scratch. Sanded for wider joints, because the sand stops the grout shrinking and cracking as it cures.
Why does tile size change grout use so much?
Grout fills the joints, and small tiles mean many more joints per square foot. A 2 inch mosaic can use several times the grout of a 24 inch tile over the same area.
Can I keep leftover grout?
Dry grout keeps well in a sealed bag in a dry place and is handy for future repairs. Mixed grout cannot be saved - only mix what you can use in about 30 minutes.