Free tile grout calculator: enter tile size, thickness, joint width and area to get grout weight, bags needed and coverage per bag for any tiling job.
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Enter your values and press Calculate.
Enter one tile length and width in inches, the tile thickness (which sets joint depth), the grout joint width, the total area to grout in square feet, your bag size and a waste allowance. The calculator works out grout weight per square foot from joint volume and grout density, then gives total grout, grout with waste, whole bags needed and coverage per bag.
Grout fills the joints around every tile, so the amount depends on joint volume, not on area alone. Each tile contributes joints along two sides, giving a joint length of tile length plus tile width. Joint volume per square foot is 144 times (tile length plus tile width) times joint width times tile thickness, divided by tile length times tile width, in cubic inches. Multiplying by grout density, about 0.0578 pounds per cubic inch (100 pounds per cubic foot for sanded grout), gives pounds per square foot. Total grout is that rate times area, plus a waste allowance for spillage and mixing loss. This is the same structure as the Tile Council of North America coverage formula competitors use, with density stated openly so you can check it.
Measure one tile in inches, including thickness, and measure the joint width you plan to use, not the width you hope for. Enter the total area to grout, choose your bag size (25 lb bags are the common retail size, with 10 lb and 50 lb bags also sold), and keep the default 10 percent waste allowance (waste factor) unless your job is unusually simple. The results show grout weight, grout with waste, whole bags rounded up, and coverage per bag, so you can compare bag sizes before you buy.
Coverage per 25 lb bag falls fast as tiles get smaller or joints get wider, because small tiles have far more joint length per square foot. A 12 × 12 inch tile with 1/8 inch joints covers roughly 384 square feet per 25 lb bag at 3/8 inch thickness, while a 2 × 2 mosaic with the same joints covers only about 96 square feet per bag. A 12 × 24 inch tile stretches further again, and a 24 × 24 inch tile further still. Mosaics need several times more grout per square foot than large format tile, which is why mosaic jobs surprise first time tilers on material cost. This grout estimator table is the quick way to sanity check the calculator result before ordering. Brand coverage charts from Laticrete and Mapei follow the same joint-volume logic, with small brand differences in stated density, which is why checking your product packaging matters.
Sanded grout contains fine sand and suits joints wider than 1/8 inch (3 mm), including most floors, because the sand gives strength under foot traffic. Unsanded grout is smoother and suits joints under 1/8 inch and delicate surfaces such as polished marble and glass, which sand could scratch. Epoxy grout is stain resistant and suits showers, wet areas and high traffic zones, but it costs more and is harder to work. Joint width therefore decides grout type as well as quantity: measure the joint first, then choose the product, then calculate.
Take 12 × 12 inch tiles, 0.375 inch thick, with 0.125 inch joints over 100 square feet, using 25 lb bags and 10 percent waste. Coverage = 144 × 24 × 0.125 × 0.375 / 144 × 0.0578 = 0.065 pounds per square foot. Total grout = 0.065 × 100 = 6.5 lb. With waste, 6.5 × 1.10 = 7.15 lb, so bags needed = 7.15 / 25, rounded up to 1 bag, and coverage per bag = 25 / 0.065 = 384.47 square feet. For a 50 square foot mosaic job with 2 × 2 tiles, the same steps give 13.0 lb, 14.31 lb with waste, and 1 bag.
Running out mid-job risks a visible color mismatch, because a new batch can mix slightly differently, so always buy the waste allowance and keep one spare bag for future repairs. Using tile thickness as joint depth is correct only when joints are filled full depth; shallow fills use less grout but weaken the joint. Forgetting waste is the classic error: spillage, bucket residue and cuts consume 10 to 15 percent. Finally, check the coverage printed on your chosen product, since brands vary, and buy all bags from the same batch where possible.
With 12 × 12 tile and 1/8 inch joints, about 6.5 lb before waste and 7.15 lb with 10 percent waste, so 1 bag of 25 lb grout. With 6 × 6 tile it is closer to 17 lb, and 2 × 2 mosaic jumps past 50 lb per 100 square feet, because smaller tiles mean far more grout line.
It gives a close estimate from your exact tile size, thickness, joint width and area, using joint volume and standard sanded grout density. Always buy slightly more than the calculated amount to account for waste, mixing and future repairs, and check your product packaging for its own coverage figure.
Yes, wider joints require much more grout, because joint volume grows directly with joint width. Measure the intended spacing accurately with spacers, and keep joints uniform across the whole surface rather than varying them to match tile edges.
Yes, the calculator works for any flat tiling project, including floors, walls and backsplashes, as long as you enter the right tile thickness and joint width for that surface.
Use 1/16 inch (1.5 mm) for rectified tiles, 1/8 inch (3 mm) for standard ceramic, 3/16 inch (5 mm) for natural stone, and 1/4 inch (6 mm) for handmade or rustic tiles. Larger gaps need sanded grout; smaller joints use unsanded grout.
Use sanded grout for floors and joints wider than 1/8 inch, since unsanded grout lacks strength for foot traffic and cracks in wide joints. Use unsanded grout for walls, glass and joints under 1/8 inch, where a smooth finish matters and scratching is a risk.
Divide grout with waste by your bag size and round up; the calculator does this for you. For 100 square feet of 12 × 12 tile at 1/8 inch joints, 1 bag of 25 lb grout is enough, while mosaic or wide-joint jobs can need several bags for the same area.
Enter the exact measurement in inches, using decimals: 1/16 inch is 0.0625, 1/8 inch is 0.125, 3/16 inch is 0.1875 and 1/4 inch is 0.25. The formula works for any rectangular tile size, not only standard sizes.