Grout Calculator
Calculate the pounds of grout your tile job needs from joint size.
What you'll need to order
- sanded or unsanded grout
- grout float
- grout sealer
- sponges
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
lb/ft² = (tile L + tile W) × joint width × tile thickness × (144 ÷ tile area) × 0.0451
Each tile carries half its perimeter in joints, which is why the formula uses length plus width rather than the full perimeter. Grout weighs about 0.0451 lb per cubic inch once mixed.
Worked example
With area to grout 120 sq ft, tile length 12 in, tile width 12 in, joint width 0.125 in, tile thickness 0.3125 in, this calculator returns 5.58 lb.
Waste allowance
The headline figure includes a 10% allowance for waste and over-ordering. The exact requirement is shown alongside it.
Grout needed by tile size
Figures below assume area to grout 100 sq ft × tile width 12 in × joint width 0.125 in × tile thickness 0.3125 in. Change any measurement in the calculator to get your own numbers.
| Tile length | Grout needed (lb) | 25 lb bags (bags) |
|---|---|---|
| 2 in | 16.28 | 0.65 |
| 4 in | 9.30 | 0.37 |
| 6 in | 6.98 | 0.28 |
| 12 in | 4.65 | 0.19 |
| 18 in | 3.88 | 0.16 |
| 24 in | 3.49 | 0.14 |
| 36 in | 3.10 | 0.12 |
Per 100 sq ft with a 1/8 in joint. Smaller tiles mean more joint length per square foot, which is why mosaic sheets use several times the grout of a large-format tile.
Grout for common tiling jobs
| Job | Size | Grout needed |
|---|---|---|
| Shower wall, 4x4 in tile | 90 sq ft × 4 in × 4 in × 0.125 in × 0.25 in | 10.05 lb |
| Bathroom floor, 12x12 in | 45 sq ft × 12 in × 12 in × 0.125 in × 0.3125 in | 2.09 lb |
| Kitchen backsplash, subway | 30 sq ft × 6 in × 3 in × 0.0625 in × 0.25 in | 1.67 lb |
| Open-plan floor, 24x24 in | 400 sq ft × 24 in × 24 in × 0.1875 in × 0.375 in | 16.74 lb |
| Patio, 16x16 in porcelain | 200 sq ft × 16 in × 16 in × 0.25 in × 0.5 in | 22.32 lb |
Buy at least one full bag more than the calculation. Mixing a partial bag to match an existing batch almost never gives the same colour once cured.
Grout joint widths and where they belong
| Type | Joint width (in) | Notes |
|---|---|---|
| Rectified large-format tile | 0.06 | 1/16 in; unsanded grout only |
| Standard wall tile | 0.13 | 1/8 in; the most common joint |
| Standard floor tile | 0.19 | 3/16 in; sanded grout |
| Rustic or handmade tile | 0.25 | 1/4 in; absorbs dimensional variation |
| Exterior paver | 0.38 | 3/8 in; allows for movement |
Use unsanded grout below 1/8 in and sanded at 1/8 in and above. Sanded grout in a very narrow joint will not pack properly; unsanded in a wide joint shrinks and cracks.
Frequently asked questions
How much grout do I need per square foot?
It depends far more on tile size than on area. A 12x12 in tile with a 1/8 in joint needs roughly 0.5 lb per square foot; a 4x4 in tile at the same joint needs about three times that.
How many square feet does a 25 lb bag of grout cover?
About 100 sq ft of 12x12 in tile with a 1/8 in joint, but only 30 to 40 sq ft of small mosaic. Always work it out from your actual tile size.
What is the difference between sanded and unsanded grout?
Sanded grout contains silica that resists shrinkage in wide joints. Unsanded is smoother and belongs in joints under 1/8 in, and on polished stone that sand would scratch.
Should I use epoxy grout?
It is worth it in showers, on kitchen worktops and anywhere staining matters, because it is effectively waterproof and never needs sealing. It costs several times as much and sets fast, which makes it unforgiving to work with.
How much grout do I need for 100 square feet?
For 12 by 12 tile with a 1/8 inch joint, about 4 lb. Smaller tiles need far more — the same area in 6 by 6 tile takes over 8 lb because there is twice the joint length.
Should I use sanded or unsanded grout?
Sanded for joints 1/8 inch and wider, unsanded for anything narrower. Unsanded grout shrinks and cracks in a wide joint; sanded grout will scratch polished stone and glass tile.
Why does tile size change how much grout I need?
Grout fills the joints, and smaller tiles mean more joints per square foot. Halving the tile dimension roughly doubles the grout required for the same area and joint width.
Does grout need sealing?
Cement-based grout does, in wet areas and on floors — reseal every year or two. Epoxy grout needs no sealer at all but is considerably harder to work with and costs several times more.