How Much Grout Do I Need?
Enter your tile size, joint width, and total area to find out exactly how many bags of grout to buy — with waste included.
Project Area
Tile Size
How to Calculate Grout Needed
The amount of grout depends on tile size, joint width, tile thickness, and grout type density. The industry-standard formula from the TCNA Handbook calculates total joint volume, converts it to pounds using grout-specific density, adds a 10% waste buffer, then divides by your bag size for an exact count.
Key insight: Joint width has far more impact than tile size. A ¼" joint uses roughly twice as much grout as a ⅛" joint on the same tile. Always buy at least 10% extra — grout is sold in production batches, and color can vary between batches.
Sanded vs. Unsanded vs. Epoxy Grout
| Type | Best For | Joint Width | Sealing Required? |
|---|---|---|---|
| Sanded | Floors, large-format tiles, natural stone | ⅛" and wider | Yes — annually |
| Unsanded | Wall tiles, polished stone, glass, small joints | Under ⅛" | Yes — annually |
| Epoxy | Showers, kitchens, pools, commercial | Any width | No — stain-proof |
Never use sanded grout on polished marble or glass tile — the sand particles will permanently scratch the surface. Use unsanded or epoxy for those applications.
Grout Quick Reference by Tile Size
| Tile Size | Joint Width | ~Lbs per 100 sq ft | 10 lb bags needed |
|---|---|---|---|
| 4×4" | ⅛" | ~18 lbs | 2 bags |
| 6×6" | 3/16" | ~14 lbs | 2 bags |
| 12×12" | ¼" | ~11 lbs | 2 bags |
| 12×24" | ¼" | ~9 lbs | 1 bag |
| 18×18" | ⅜" | ~10 lbs | 1 bag |
| 24×24" | ¼" | ~7 lbs | 1 bag |
| 2×2" mosaic | ⅛" | ~35 lbs | 4 bags |
All figures per 100 sq ft, including 10% waste. Actual usage varies by tile porosity, joint depth, and application technique. Always confirm with the product data sheet for your specific grout brand.
Mixing: Water Ratio, Small Batches, and Pot Life
Knowing how many bags to buy is only half the job. The other half is how much of a bag to mix at once, and how much water goes with it — and this is where most grout problems start, because grout that is mixed wrong fails no matter how good the tile work is.
| Amount of powder | Water (approx.) | Covers roughly |
|---|---|---|
| 25 lb bag (full) | 1 to 1¼ quarts | Whole floor or large wall |
| 10 lb bag (full) | 14 to 19 fl oz | Small bathroom floor |
| 5 lb | 7 to 9 fl oz | A backsplash section |
| 1 lb | 1½ to 2 fl oz | A few repair tiles |
Treat these as a starting point and check the bag, because the ratio varies by product and sanded grout takes slightly more water than unsanded. Manufacturers print the figure for a full bag only, which is why a partial batch needs the per-pound number above.
Mixing a small batch. Weigh the powder rather than guessing by volume — a scoop of grout varies in density enough to throw off the ratio. Put the water in the bucket first, then add powder to the water, never the reverse. Powder added to water disperses; water added to powder traps dry lumps in the middle that you will not find until they streak the joints.
Slake, then stir again. Mix to a stiff peanut-butter consistency, let it rest 5 to 10 minutes so the polymers hydrate, then re-stir without adding water. Grout always stiffens during slaking and it is meant to. Adding water at that point is the most common way to end up with joints that cure pale, powdery, and prone to cracking, because the extra water breaks the cement ratio permanently.
Pot life. Mix only what you can install in about 30 minutes for cement grout. Epoxy is quoted at 45 to 90 minutes but gets noticeably harder to work well before that, and it cannot be revived at all. On a large floor, mixing three small batches beats mixing one large one and fighting the last third of it.
Very small repairs. Below about half a pound, the ratio is hard to hit accurately and a pre-mixed tub is usually the better answer despite costing more per pound. Pre-mixed grout is also the practical choice for craft-scale work such as a coaster or a mosaic tray, where a mixed batch would be almost entirely waste.
Working in metric? One pound is 0.454 kg and one US quart is 0.946 litres, so a 25 lb bag is about 11.3 kg taking roughly 1 litre of water. For volume-based estimates, 1 cubic metre is about 35.3 cubic feet.
Grout Cost by Type (2026)
| Grout Type | 10 lb bag | 25 lb bag | Notes |
|---|---|---|---|
| Sanded cement | $10–$18 | $22–$35 | Most affordable, seal annually |
| Unsanded cement | $12–$20 | $25–$38 | For narrow joints and wall tile |
| Epoxy (2-part) | $30–$50 | $60–$90 | No sealing, stain-proof, harder to apply |
Frequently Asked Questions
How much grout do I need for 100 sq ft of tile?
For a 12x12 inch tile with a 1/8 inch joint, expect roughly 2-3 bags (25 lb each) of sanded grout per 100 sq ft — smaller tiles or wider joints need significantly more.
What's the difference between sanded and unsanded grout?
Sanded grout is for joints 1/8 inch and wider. Unsanded is for joints narrower than 1/8 inch and for polished stone or glass tile, which sanded grout can scratch.
How does joint width affect grout quantity?
Wider joints use significantly more grout — going from a 1/8 inch to a 1/4 inch joint can roughly double the amount needed for the same tile area.
Should I buy extra grout for a custom color?
Yes, always buy one extra bag. Custom or discontinued colors can vary between production batches, so running short mid-project risks a visible mismatch.