How much grout do I need?
100 sq ft of 12x12 tile at 1/8 in joints takes about 17.2 lb — one 25 lb bag.
Tile size matters more than area. The same 100 sq ft in 2x2 mosaic needs 3 bags, because small tiles mean far more joint per square foot.
Grout for 100 sq ft, by tile
| Tile | Joint | Grout | 25 lb bags | Coverage per bag |
|---|---|---|---|---|
| Mosaic (1x1, 2x2) | 1/16 in | 34.4 lb | 2 | 73 sq ft |
| Subway 3x6 | 1/16 in | 21.5 lb | 1 | 116 sq ft |
| 4x4 | 1/16 in | 17.2 lb | 1 | 145 sq ft |
| 6x6 | 1/8 in | 28.7 lb | 2 | 87 sq ft |
| 8x8 | 1/8 in | 25.8 lb | 2 | 97 sq ft |
| 12x12 | 1/8 in | 17.2 lb | 1 | 145 sq ft |
| 12x24 | 3/16 in | 19.4 lb | 1 | 129 sq ft |
| 18x18 | 1/8 in | 13.4 lb | 1 | 187 sq ft |
| 24x24 | 3/16 in | 15.1 lb | 1 | 166 sq ft |
| 24x48 | 3/16 in | 11.3 lb | 1 | 221 sq ft |
Assumes 0.375 in thick tile. Thicker tile means deeper joints and proportionally more grout — a 3/4 in paver at the same joint width takes twice what the table says.
The formula, and why bag coverage looks wrong
Every tile owns half of each joint around it, which reduces to a joint length of (L + W) ÷ (L × W) per unit area. Multiply by the joint width and the tile thickness and you have the volume:
grout per sq ft = 144 × (L + W) ÷ (L × W) × joint × thickness
For 12x12 tile at 1/8 in and 0.375 in thick, that is 1.12 cubic inches per square foot.
Work that through to weight and you will get a coverage roughly twice what the bag claims. The bag is right and the geometry is right — the gap is mixing loss, joints filled proud and struck back, and the last of a batch going off before it is used. Buy to the bag, not to the arithmetic, and keep the spare: grout from a different lot rarely matches.
Common questions
- How much grout for 50 square feet?
- Half the table: about 8.6 lb for 12x12 at 1/8 in, so one bag. Grout is sold in sizes that overshoot small jobs — a bag is usually the minimum whatever the area.
- How much grout for a shower?
- A standard 3 ft x 5 ft shower with walls to 6 ft is roughly 100 sq ft of surface once you count three walls and the floor. In 4x4 wall tile with 1/16 in joints that is 1 bags, plus more for the floor if it is mosaic — mosaic shower floors eat grout at 36 sq ft per bag.
- How much grout for a backsplash?
- A typical kitchen backsplash is 25 to 35 sq ft. In 3x6 subway with 1/16 in joints, that is comfortably one bag — 116 sq ft per bag at that size.
- How much grout per square metre?
- Divide the coverage figures by 10.76. A bag covering 145 sq ft of 12x12 covers about 13 m².
- Sanded or unsanded?
- Sanded for joints 1/8 in and wider, unsanded below that. Unsanded in a wide joint shrinks and cracks; sanded in a narrow one will not pack in, and the sand can scratch polished stone and glass.
- Should I buy extra?
- One spare bag, from the same lot. Colour varies between production runs enough to see, so a repair grouted two years later with a fresh bag shows as a patch even with the same product code.
Related answers
Or work out the area first with the tile calculator.