Grout Calculator
Estimates only. Grout density and bag yield vary by product — confirm both on your bag's coverage chart before ordering.
Grout is estimated by joint volume, not floor area: the wider and deeper your joints and the smaller your tiles, the more you need. A 100 sq ft floor in 12 × 12 tile with a 1/8 in joint takes only a few pounds of grout, while the same floor in small mosaic can take several times that. Enter your area, tile size, joint width, and joint depth below for grout volume, weight, and bags to buy.
Grout use by tile size
| Tile size | Joint is % of surface | Grout volume / 100 sq ft | Approx. lb / 100 sq ft | Notes |
|---|---|---|---|---|
| 2" × 2" mosaic | 11.4% | 0.24 ft³ | 24 lb | Small tile = most joint, most grout |
| 4" × 4" | 6.0% | 0.12 ft³ | 12 lb | Wall and accent tile |
| 3" × 6" (subway) | 6.0% | 0.12 ft³ | 12 lb | Backsplashes, wall tile |
| 6" × 6" | 4.0% | 0.08 ft³ | 8 lb | Floor and wall tile |
| 12" × 12" | 2.1% | 0.04 ft³ | 4 lb | Standard floor tile |
| 12" × 24" | 1.5% | 0.03 ft³ | 3 lb | Large-format floors |
| 18" × 18" | 1.4% | 0.03 ft³ | 3 lb | Large open-room floors |
| 24" × 24" | 1.0% | 0.02 ft³ | 2 lb | Large tile = least grout |
How to estimate grout
Grout fills the joint channel around every tile, so the amount you need depends on the joint size and the tile size, not just the floor area. For one tile-plus-joint cell, the grout is everything inside the cell except the tile face: 1 − (tile face ÷ (tile + joint) footprint). Multiply that fraction by your surface area and by the joint depth (normally the tile thickness) to get grout volume, then convert to weight and bags. Small tiles have far more joint per square foot than large tiles, which is why a mosaic floor drinks grout and a large-format floor barely uses any. If you still need the tile count itself, run the tile calculator first, then come back here for grout.
Joint width and depth drive everything
Doubling the joint width roughly doubles the grout; doubling the joint depth doubles it exactly. Joint depth is normally your tile thickness, since grout is packed flush to the tile face — a 1/4-inch-thick tile gives a 1/4-inch joint depth. Use unsanded grout for joints 1/8 inch and narrower and sanded grout for wider joints, since sand keeps wide joints from shrinking and cracking. Setting natural stone instead of tile? The stone calculator sizes the material by tonnage and type.
Volume is exact; bags depend on the product
The grout volume this calculator gives is exact geometry. Turning volume into bags needs the grout's density and the dry weight per bag, and both vary by product — sanded, unsanded, and epoxy grouts differ, and so does how wet you mix it. The density and bag-weight fields are prefilled with a common cementitious figure, but the coverage chart on your actual bag is the number to trust — enter it and the bag count follows. Most products list a mixing ratio (water or activator to powder) on the bag; follow it exactly, since over-watering weakens the joint and changes how far a bag goes.
Cementitious vs epoxy grout
The joint volume this calculator gives is the same whichever grout you pick — it's pure geometry — but the two grout families turn that volume into product very differently.
- Cementitious grout is the standard powder you mix with water, sold by dry weight in 8, 10, and 25 lb bags. It's the cheaper option and comes in sanded and unsanded forms (below). It's porous, so it needs sealing to resist stains and moisture. The prefilled density and bag-weight fields assume this type.
- Epoxy grout is a resin, hardener, and colored filler that cure by chemical reaction, sold as multi-part kits rated for a square-foot range at a given tile and joint size — not by the pound. It's waterproof, stain-resistant, and needs no sealing, which suits showers, backsplashes, and commercial kitchens, but it can cost up to about five times as much as cementitious and sets fast. To size it, take the joint volume here, then match it to the coverage the kit lists for your tile size rather than the pound-based bag count.
Sanded vs unsanded coverage
Within cementitious grout, the sanded-versus-unsanded choice is set by joint width: unsanded for joints 1/8 inch and narrower, sanded for wider joints, since the aggregate in sanded grout resists the shrinking and cracking that plagues wide joints. Unsanded is smoother and won't scratch polished stone or glass in tight joints. It doesn't change the joint volume you calculated, but sanded grout is bulked out with sand, so it generally covers more area per pound and costs less than unsanded — one more reason to trust the coverage figure on your specific bag over any default.
Common mistakes
- Estimating grout by floor area alone. Two floors of the same size can need wildly different grout — mosaic versus large-format can differ by 5× or more. Always factor in tile size and joint dimensions.
- Forgetting joint depth. Thicker tiles have deeper joints and use proportionally more grout. Don't assume a fixed depth; use your tile's actual thickness.
- Trusting a generic density. Epoxy and sanded grouts have different yields. The bag's own coverage chart beats any default.
- Mixing too much at once. Grout stiffens in the bucket. Mix in batches you can place before it sets, and keep the overage for the batch that inevitably goes off early.
Frequently asked questions
How do I calculate how much grout I need?
Grout fills the joint channel around every tile, so the amount depends on four things: your total area, the tile size, the joint width, and the joint depth (usually the tile thickness). The volume is the share of the surface taken up by joints rather than tile face, multiplied by how deep those joints run. Smaller tiles and wider or deeper joints need more grout; large tiles with thin joints need very little. Enter your numbers above for exact volume, weight, and bags.
How much grout do I need for 100 square feet?
For 100 sq ft of standard 12 × 12 in tile with a 1/8 in joint and 1/4 in depth, you need only about 0.04 cubic feet of grout — roughly 4 pounds, well under one standard bag. Drop to small 2 × 2 mosaic and the same area needs about six times as much, because tiny tiles have far more joint per square foot. Tile size is the biggest driver, so always calculate for your actual tile rather than using a flat per-100-sq-ft rule.
What is joint depth and what should I enter?
Joint depth is how deep the grout is packed into the gap between tiles, and it's normally equal to your tile thickness because grout is filled flush to the tile face. Most floor tile is 1/4 to 3/8 in thick and wall tile is often 1/4 in, so those are typical depths to enter. If you're only grouting a partial depth, enter that instead. Depth scales the volume directly — doubling it doubles the grout.
Does tile size change how much grout I need?
Yes, and it's the single biggest factor. Small tiles pack far more joint length into each square foot, so they use dramatically more grout than large-format tiles. At a 1/8 in joint, 2 × 2 in mosaic uses roughly six times the grout of a 12 × 12 in tile over the same area, and large-format 24 × 24 in tile uses about half again less than that. Always run the numbers for your specific tile size.
How many bags of grout do I need?
Divide the total grout weight your job needs by the pounds of dry grout per bag, then round up to whole bags. Bag sizes vary — common dry grout comes in 8, 10, and 25 lb bags — so check the weight printed on the product. Because most jobs need only a fraction of a bag, buy at least one full bag and keep the leftover sealed for repairs. The calculator rounds up to whole bags for you once you enter the bag weight.
Should I use sanded or unsanded grout?
Use unsanded grout for joints 1/8 in and narrower, and sanded grout for wider joints. Sanded grout contains aggregate that resists shrinking and cracking in wide joints, while unsanded is smoother and won't scratch delicate surfaces like polished stone or glass in tight joints. This choice doesn't change the volume you need, but it does change the product's density and coverage, so confirm the coverage figure on the specific bag you buy.
How much extra grout should I buy for waste?
Add about 10% for mixing and cleanup loss — grout that stiffens in the bucket before you can use it, plus what stays on the float and gets wiped away. Grout waste is smaller than tile waste because there are no offcuts, but it's real, especially on large jobs mixed in batches. Since most jobs need less than a full bag anyway, rounding up to the next whole bag usually covers the overage on its own.
Why is my grout coverage different from the bag's estimate?
Manufacturer coverage charts assume a specific tile size, joint width, and joint depth, so their square-feet-per-bag figure only matches your job if all three match theirs. Change to smaller tile, a wider joint, or a deeper joint and real coverage drops fast. This calculator works from your actual dimensions instead of a fixed chart, but the conversion from volume to bags still depends on the density and bag yield of your specific product — confirm both on the label.
What's the difference between epoxy and cementitious grout?
Cementitious grout is a cement powder you mix with water, sold by dry weight in bags; it's cheaper, comes in sanded and unsanded forms, and needs sealing because it's porous. Epoxy grout is a resin and hardener that cure by chemical reaction, sold as multi-part kits rated for a square-foot range rather than by the pound; it's waterproof, stain-resistant, and needs no sealing, which suits showers and backsplashes, but it can cost up to five times as much and sets fast. The joint volume is the same for both — only the way you buy and price the product changes, so for epoxy match the volume to the kit's coverage range instead of a pound-based bag count.
Is this the same as a non-shrink grout calculator?
No. This calculator is for tile grout that fills the joints between tiles. Non-shrink grout is a structural product poured under steel baseplates, columns, and machine bases to transfer load, and it's estimated by the void volume you're filling, not by tile size and joint width. If you're grouting tile, you're in the right place; for a structural pour, size it by the length, width, and depth of the cavity instead.
Related calculators
Sources
- Grout CalculatorOmni CalculatorCorroborates the joint-volume method — grout needed is driven by tile size, joint width, and joint depth — and that small tiles with wide joints consume far more grout per square foot than large-format tile.
- Grout Joint Recommendations and Sanded vs. Unsanded GroutCustom Building ProductsManufacturer guidance that unsanded grout is used for joints 1/8 in and narrower and sanded grout for wider joints, and that published coverage assumes a specific tile size, joint width, and depth.
- Comparison of Two Specifications for Cementitious GroutsMC-BauchemieCorroborates that epoxy grouts offer low water absorption, higher compressive strength, and chemical resistance but can cost up to five times as much as more widely used cementitious grout.