Grout Calculator
Estimate sanded, unsanded, or epoxy grout in pounds, bags, or units from your tile size, joint width, and area.
For several surfaces, add them up and enter the total tiled area.
For mosaic sheets, enter the individual tile size, not the sheet.
This is the joint depth. Measure the edge of your tile.
Sanded for 1/8 in and wider, unsanded for 1/8 in and under, epoxy for any width.
Cement grout is sold by weight, epoxy by unit. Match this to your grout type.
Your Grout Estimate
- Enter your tiled area - length times width in feet; for several surfaces, add them up.
- Enter your tile size - length and width in inches. For mosaic sheets, use the individual tile size, not the sheet.
- Set thickness and joint width - thickness is the joint depth; 1/8 in is the standard joint for most floor tile.
- Pick the grout type - sanded for 1/8 in and wider, unsanded for 1/8 in and under, epoxy for any width.
- Choose your bag or unit size - then buy the amount shown, all from one lot, with a little spare.
How much grout you need depends on three things: tile size, joint width, and tile thickness (which sets how deep the joint is). A 100 sq ft floor of 12 x 12 in tile with 1/8 in joints takes only about 8 lb of sanded grout, well under one 25 lb bag, because the joints are a small fraction of the surface. Smaller tiles and wider joints raise that fast: the same floor in 2 x 2 in mosaic needs around five times as much. Enter your area, tile size, and joint width above for an exact figure in pounds, bags, or epoxy units.
What Grout Has to Fill
Grout Coverage by Tile Size
These are Custom Building Products coverage figures for one 25 lb bag of sanded grout, in square feet per bag. Larger tiles and tighter joints stretch a bag further; small tiles and wide joints burn through it. The calculator above works the math for your exact tile, thickness, and joint:
| Tile size | 1/8 in joint | 3/16 in joint | 1/4 in joint |
|---|---|---|---|
| 2 x 2 in mosaic | 96 ft² | 68 ft² | 54 ft² |
| 6 x 6 in | 266 ft² | 181 ft² | 139 ft² |
| 12 x 12 in | 348 ft² | 234 ft² | 177 ft² |
| 12 x 24 in | 461 ft² | 310 ft² | 234 ft² |
| 18 x 18 in | 518 ft² | 348 ft² | 262 ft² |
| 24 x 24 in | 688 ft² | 461 ft² | 348 ft² |
How Grout Quantity Is Figured
Grout sits in the joints, so the amount you need is a volume: joint width times joint depth times the total length of every joint in the installation. The joint depth is the tile thickness, since grout fills the gap from the tile surface down to the thinset. Measure the tiled area, or pull it straight from the Tile Calculator if you are still planning the layout, then enter your tile size and joint width and the calculator solves the geometry for you.
Tile size is the part most people underestimate. A small tile packs far more joint length into each square foot than a large one, so mosaics and small mosaics use several times the grout of a 12 x 12 in or 24 x 24 in floor at the same joint width. Once the joint volume is known, the calculator converts it to weight using the grout density (sanded is about 112 lb/ft³, non-sanded about 108) and rounds up to whole bags, or for epoxy it divides by the unit volume and rounds up to whole units.
Sanded, Unsanded, and Epoxy Grout
Grout type is set by joint width first, then by the tile surface and how much abuse the joint will take:
| Type | Joint range | Best for | Watch out for |
|---|---|---|---|
| Sanded cement | 1/8 in to 1/2 in | Floors, most walls, wider joints | Sand scratches polished stone and glass |
| Unsanded cement | 1/16 in to 1/8 in | Narrow joints, polished stone, glass | Cracks if forced into a wide joint |
| Epoxy | Any width | Wet areas, stain and chemical resistance | Shorter working time, higher cost, sold by unit |
At exactly 1/8 in, either cement grout works; sanded is the more common floor choice and unsanded is the safer pick on a polished or glass surface. Epoxy needs no sealing and resists staining, which suits showers and kitchens, but it sets fast and is less forgiving to work, so most DIYers reserve it for smaller, high-value areas.
Why Most Grout Calculators Tell You to Buy Too Much
Many grout calculators report two to three times the grout a job actually needs. The usual cause is a density set far too high, near 0.18 lb per cubic inch (over 300 lb/ft³), when cured grout really weighs about 105 to 125 lb/ft³. The figures here are calibrated to the manufacturer coverage charts and match them to the pound, which is why the bag count often looks lower than you expected. It is correct: a typical bathroom floor needs a few pounds of grout, not a stack of bags.
Over-buying only wastes money, but the bigger risk runs the other way. If you trust a low estimate, run short, and open a second bag from a different color lot, the new grout can finish a slightly different shade, since cement grout color shifts between lots and with how much water you mix in. That difference shows up as a stripe across the floor. Buy the accurate amount in one lot, mix each batch the same way, and keep a little spare for repairs.
Grout Formula
The exact method uses the geometry of the joints, not a flat per-square-foot rule. L and W are the tile length and width, j is the joint width, and the tile thickness is the joint depth (all in inches; area in square feet):
Joint volume (in³) = Joint fraction × tile thickness × (area × 144)
Cement grout (lb) = Joint volume × density (sanded 0.0648, unsanded 0.0625)
Bags = Grout lb × (1 + waste) ÷ bag weight, rounded up
Epoxy units = Joint volume × (1 + waste) ÷ unit volume, rounded up
The joint-fraction step is what makes small tiles take so much more grout: as the tile dimension shrinks toward the joint width, the fraction climbs. A flat (L + W) ÷ (L × W) shortcut over-predicts on mosaics, so this calculator uses the exact form above.
Worked Examples
Master bathroom floor: 80 sq ft of 12 x 12 in porcelain, 3/8 in thick, with 3/16 in joints in sanded grout. The joints come to about 132 cubic inches, which is 8.5 lb of grout, or 9.4 lb with 10% waste. That is one 25 lb bag with most of it left over, so a 7 lb bag would also cover the job. Buy one, keep the spare, and use a single lot.
Subway tile shower wall: 60 sq ft of 3 x 6 in tile, 1/4 in thick, with tight 1/16 in joints in unsanded grout. That works out to about 4.1 lb, or 4.5 lb with waste, well inside one 10 lb box. Unsanded is correct here because the joints are under 1/8 in and the smooth mix suits a glazed wall tile.
Large-format porcelain floor: 200 sq ft of 24 x 24 in tile, 1/2 in thick, with 1/16 in joints in epoxy. The joint volume is about 75 cubic inches, which fits inside a single SpectraLOCK PRO Full Unit at 189 cubic inches. Large tiles with tight joints use very little grout, but epoxy is sold by the unit, so you buy one whole unit.
By contrast, a 25 sq ft glass mosaic accent in 2 x 2 in tile with 1/8 in joints needs about 6.4 lb, nearly as much grout as the 80 sq ft porcelain floor above, on less than a third of the area, because the small tiles pack in far more joint length.
Sources & Standards
- Cement-grout figures are calibrated to Custom Building Products Polyblend coverage charts (sanded about 112 lb/ft³, non-sanded about 108 lb/ft³), so bag counts track the manufacturer published coverage rather than a generic density.Custom Building Products TDS-129 / TDS-130
- Epoxy is figured by unit volume from LATICRETE SpectraLOCK PRO data: about 189 cubic inches per Full Unit and 47 per Mini Unit. Other epoxy brands package and yield differently, so confirm the unit on the product you buy.LATICRETE SpectraLOCK PRO coverage data (DS 254.3)
- Joint width follows ANSI A108.02, which calls for a joint at least three times the tile facial-dimension variation and never under 1/16 in. Sanded suits joints 1/8 in and wider; unsanded is for 1/8 in and under and for surfaces sand would scratch. Movement joints at perimeters and changes of plane are caulked, not grouted, per TCNA EJ171.TCNA Handbook; ANSI A108.02, A118.6/.7, A108.10
Around the Tile Job
Grouting is the last step of a tile install. The jobs around it:
Related Calculators
Pair this with the rest of the surface tools. See the full surface calculator collection for tile, flooring, paint, and more.
Frequently Asked Questions
How much grout do I need per square foot?
It depends mostly on tile size and joint width, not a single fixed number. A 12 x 12 in floor tile with 1/8 in joints uses only about 0.07 lb per square foot, while 2 x 2 in mosaic with the same joint uses around 0.4 lb, roughly five to six times more. Enter your tile size and joint width above for an exact figure.
How much grout for a 100 sq ft floor?
For 100 sq ft of 12 x 12 in tile with 1/8 in joints in sanded grout, about 8 lb, which is under one 25 lb bag. Smaller tiles or wider joints raise that quickly; a 100 sq ft mosaic floor can need 40 lb or more. Run the calculator with your exact tile and joint size.
What is the difference between sanded and unsanded grout?
Sanded grout has fine sand for strength and is used in joints 1/8 in and wider, up to about 1/2 in. Unsanded is smooth and is used in joints 1/8 in and under, and on polished stone or glass that sand would scratch. Forcing unsanded into a wide joint can crack it; using sanded on glass can scratch the surface.
Do I need sanded or unsanded grout for 1/8 inch joints?
Either works at exactly 1/8 in, which is the crossover point. Sanded is the more common choice for 1/8 in floor joints, while unsanded is fine at 1/8 in on walls and is the better pick if the tile is polished stone or glass. For anything wider than 1/8 in use sanded; for anything narrower use unsanded.
How much extra grout should I buy for waste?
Add about 10% for mixing, cleanup, and uneven joints, which this calculator does by default. Add 12% to 15% for unglazed or quarry tile, since porous tile pulls extra grout during cleanup. Buy any spare from the same lot so the color matches.
Does grout color vary between bags?
Yes. Cement grout color shifts between production lots, and also with how much water you mix in, so two bags can finish slightly different shades. Buy all of your grout in one purchase from the same lot number, mix each batch the same way, and keep a little spare for future repairs.
How do I figure grout for mosaic sheets?
Enter the individual small tile size, not the 12 x 12 in sheet size. The calculator needs the real tile dimension because mosaics have far more joint length per square foot, which is why they use several times more grout than large tiles.
How is epoxy grout measured?
Epoxy grout is sold by the unit, not by weight, and each unit fills a set volume. A LATICRETE SpectraLOCK PRO Full Unit fills about 189 cubic inches of joint, and a Mini Unit is a quarter of that. The calculator gives the joint volume and rounds up to whole units. Other brands differ, so check the unit yield on your product.