Free Online Grout Calculator

Grout use per square foot depends on tile size, joint width, and joint depth. The quick method: compute the tile-to-tile-plus-gap ratio R = (l × w) / ((l + g) × (w + g)), take the unfilled share (1 − R), multiply it by the surface area to get the grout area, then multiply by joint depth for volume. As a rule of thumb, 12 × 12 in tiles with 1/8 in joints need roughly 0.04 lb of dry grout per ft² at a 1/4 in joint depth, while mosaics can need 5–10 times more.

You need about 0.02626 ft³ (0.74 L) of grout for a 50 ft² backsplash covered with 1 ft² tiles and a 5 mm gap. That is roughly 2.63 lb of dry material at the default density of 100 lb/ft³, or about 2.89 lb once a 10 % waste allowance is added — one 5 lb bag covers it with room to spare.

The dry material percentage is the share of the computed weight that is actual dry powder — the part you buy in bags. The default is 100 %, which is what you want for purchasing dry bagged grout and what manufacturer coverage tables quote (pure powder consumption). If instead you want the weight of the wet mix — cement grout is typically mixed at a 1:1 water-to-powder ratio, so half of the mixed weight is water — set this field to 50 %.

The calculator defaults to 100 lb/ft³ (1,600 kg/m³), the midpoint of the typical 85–110 lb/ft³ range for cementitious grout. Sand-heavy sanded grouts sit toward the upper end; lighter glass-bead or very fine polymer grouts toward the lower end. Epoxy grouts are denser — around 1,800–2,000 kg/m³ — and because they are sold as liquid kits you can read the result as a volume in liters or fluid ounces instead of a bag weight.

A 10 % waste allowance covers normal spills, mixing errors, and the grout left in the bucket and float. Step up to 15–20 % for mosaics, irregular or natural-stone tiles, heavily textured surfaces that steal grout from the joints, or first-time installers. The waste slider caps at 25 %, which is the practical upper bound before over-purchasing becomes the bigger problem.

Grout is sold in fixed package sizes, so the calculator rounds the recommended purchase weight up to the next whole bag and reports the coverage margin — the material left after the job. For example, if your project needs 12.4 lb and bags come in 10 lb units, you buy 2 bags and have about 7.6 lb spare. Keeping a part-bag sealed for future repairs is a feature, not a waste.

Yes — the joint depth is what turns an area into a volume, and in most installations joints are grouted flush with the tile face, so joint depth equals tile thickness. That is why the multi-room estimator asks for tile thickness: a 3/8 in thick floor tile needs roughly twice the grout of a 3/16 in wall tile at the same joint width.

The math is the same; the choice depends on joint width. Joints 1/8 in (3 mm) and wider take sanded grout, which is stronger and resists shrinking in wide joints. Joints narrower than 1/8 in take unsanded grout, which flows into tight gaps without clogging. Because sanded mixes are slightly denser, you can raise the density a few percent, but the bag count rarely changes.

Run the same volume calculation, then use the volume result instead of the weight. Epoxy grout is sold as 2-part or 3-part kits measured in liquid volume, so convert the result to milliliters or fluid ounces and divide by the kit size. Raise the density to about 1,900 kg/m³ if you want the weight of the mixed epoxy, and note that epoxy's short pot life makes precise batch planning — and the waste allowance — even more important.

For the full kit-based math — 2-part and 3-part kit conversion, pot-life batch planning and premixed bucket coverage — see the dedicated epoxy grout calculator.

Yes — a shower is just another tiled surface, so the math is identical. Measure each wall and the floor separately and enter them as their own rooms in the multi-room estimator; the project total and bag count update instantly. For wet areas, a 10–15 % waste allowance is smart practice, choose a grout rated for wet zones, and keep joint depth equal to the tile thickness just as anywhere else.

It gives a close estimate for rectangular tiles with uniform joints — typically within a few percent when the measurements are exact. Real usage shifts with tile shape, substrate waviness, thinset crowding the joints and clean-up loss, which is exactly what the waste allowance absorbs. For octagon-dot or pebble formats, treat the result as a floor value and buy slightly more — the tile shape effects section explains why.

Enter decimal inches — 0.375 for a 3/8 in joint, 0.1875 for 3/16 in, 0.125 for 1/8 in. The fraction-to-decimal chart below lists every 1/16 in step with its metric equivalent, and metric mode accepts millimeters directly. Mixed formats are fine too: a tile entered as 12.5 × 24 works just as well as fractions.

For 12 × 12 in floor tile with 1/8 in (3 mm) joints at the coverage table's 8 mm depth, figure about 0.05 lb of dry grout per ft² — roughly 5 lb net for 100 ft², or 5.6 lb once a 10 % waste allowance is added, so one 10 lb bag covers it. The same 100 ft² in 2 × 2 in mosaics needs about 29 lb net (32 lb with waste), while 24 × 24 in large-format tile needs under 3 lb. Find your tile in the coverage table above and multiply the factor by your area.

Hexagons behave like squares when measured across the flats — the same formula applies. Octagon-and-dot patterns are the big jump: the octagon fills only about 83 % of its grid cell before joints are even counted, so 2 in octagons with 1/8 in joints leave roughly 26 % of the surface to grout — about 2.5× a square tile of the same size. Pebbles and irregular mosaics can push the joint share past 30 %; use a 20–25 % waste allowance for those.

Yes. Grout shades vary between production lots (control numbers), and a wall grouted from two lots can show permanent shade bands. Buy the full bag count from a single lot, blend boxes that carry different control numbers following ANSI A108.10, and confirm the color in a test area — lighting, tile color and site conditions all shift the final shade. Keeping the coverage margin as a sealed spare from the same lot makes future repairs invisible.