Grout Calculator
Pounds and bags of grout, from tile size and joint width.
Bags to buy
2
- Grout per sq ft
- 0.113 lb
- Per 100 sq ft
- 11.3 lb
- Grout needed
- 13.6 lb
- With 10% waste
- 15.0 lb
- Bags (exact)
- 1.50
- Bags to buy (10 lb)
- 2 bags
- Grout cost
- $68.00
Buy one bag beyond the count. Running out mid-floor leaves a visible color break.
Working outside instead? Joint sand for pavers is on the paver calculator →
How this is calculated
lb per sq ft = ((L + W) ÷ (L × W)) × joint × thickness × 14.5 total lb = lb per sq ft × area × (1 + waste%) bags = ceil(total lb ÷ bag size) L, W, joint and thickness all in inches.
The (L + W) ÷ (L × W) term is joint length per square foot — it is what makes mosaic drink grout and large format sip it. The 14.5 factor converts joint volume to pounds of dry mix and matches the coverage charts printed on the bags.
Grout per 100 sq ft by tile size
At a 1/8 inch joint, before waste. Every row runs through the same function as the calculator above.
| Tile | Thickness | lb per 100 sq ft | 10 lb bags per 100 sq ft |
|---|---|---|---|
| 2" × 2" mosaic | 0.25 in | 45.3 | 5 |
| 3" × 6" subway | 0.3125 in | 28.3 | 3 |
| 4" × 4" wall | 0.25 in | 22.7 | 3 |
| 12" × 12" floor | 0.375 in | 11.3 | 2 |
| 12" × 24" plank | 0.375 in | 8.5 | 1 |
| 24" × 24" large format | 0.4375 in | 6.6 | 1 |
Frequently asked questions
How much grout do I need per square foot?
It depends on tile size far more than on area. A 12 by 12 inch floor tile with a 1/8 inch joint uses roughly 0.11 pounds per square foot, so about 11 pounds per 100 square feet. A 2 by 2 inch mosaic with the same joint uses six times that, because there is six times more joint length in the same area.
Why does small tile use so much more grout?
Grout fills the perimeter of every tile, and small tiles pack far more perimeter into the same square foot. That is the whole formula: as tile size goes up, joint length per square foot goes down. Large-format tile is the cheapest to grout and the most expensive to set.
Should I use sanded or unsanded grout?
Sanded grout is for joints of 1/8 inch and wider, where the sand resists shrinkage and cracking. Unsanded is for joints narrower than 1/8 inch, and for polished stone or glass that sand would scratch. Many modern high-performance grouts cover the whole range and drop the distinction entirely.
How much extra grout should I buy?
Buy at least one bag more than the calculation. Grout is mixed in batches and thrown away if it stiffens, tile depth varies across a real floor, and running out mid-installation means a visible color break where the batches meet. The leftover is also the only reliable color match for future repairs.
Does epoxy grout use the same quantity?
The volume of joint is identical, but epoxy is sold by unit rather than by dry pound and is roughly three to five times the price. Epoxy is worth it in showers, commercial kitchens and anywhere staining is a real risk, but it sets fast and is unforgiving to clean up, which makes it hard for a first-time installer.
Do the numbers change for a wall versus a floor?
The formula is the same, but wall tile is usually thinner, and thickness is a direct multiplier in the calculation. A 5/16 inch subway tile uses less grout per square foot than a 3/8 inch floor tile of the same face size, which is why this calculator asks for thickness rather than assuming it.
Coverage varies with how full the joints are packed, how flat the substrate is and how much grout is lost in mixing. Treat this as a planning figure and check the coverage chart on the bag you actually buy.