The short answer
- Joints 1/8" or wider: use sanded grout.
- Joints narrower than 1/8": use unsanded grout.
- Polished stone, glass, or soft-glazed tile: lean toward unsanded, or test sanded grout on a spare tile first.
At exactly 1/8", either can work. Check the joint-width range printed on the bag of the product you're considering.
What's the difference?
Both are cement-based. Sanded grout has fine sand mixed in, and unsanded grout doesn't. That one ingredient changes how each behaves.
| Sanded | Unsanded | |
|---|---|---|
| Joint width | 1/8" and wider | Narrower than 1/8" |
| Shrinking & cracking | Sand resists shrinkage in wide joints | Can shrink and crack in wide joints |
| Texture | Slightly gritty | Smooth |
| Scratch risk | Can scratch polished or glass surfaces | Low |
| Vertical surfaces | Works well | Sticky and easy to work on walls |
| Weight per joint | Denser (~104 lbs/ft³) | Lighter (~86 lbs/ft³) |
Why joint width matters
Grout shrinks slightly as it cures. In a narrow joint that isn't a problem, but in a wide joint unsanded grout can pull away from the tile edges or crack. The sand in sanded grout acts as a filler that resists that shrinkage. The reverse problem happens in tight joints: sand grains can't fit, so sanded grout won't pack in fully.
Common situations
- Floor tile (12×12", 12×24"): usually 1/8" or wider joints, so sanded.
- Subway tile backsplash: often 1/16" joints, so unsanded.
- Glass mosaic: unsanded, to avoid scratching the glass.
- Polished marble: unsanded for tight joints. Test sanded on a spare tile if the joints are wide.
- Rustic or handmade tile: wider joints to absorb size variation, so sanded.
How much of each do you need?
Sanded grout is denser, so the same joints take more pounds of sanded grout than of unsanded: roughly 20% more by weight. The calculator shows both and recommends one based on your joint width.
What about epoxy grout?
Epoxy grout is a resin-based alternative to both. It resists stains and doesn't need sealing, which makes it popular for showers and kitchens. It's more expensive and sets quickly, so it's harder to work with. Epoxy is usually sold by volume with its own coverage chart, so use the manufacturer's numbers rather than a weight-based estimate.
For the math behind grout estimates, see how much grout do I need.