Sanded vs. Unsanded Grout: How to Choose (and Why It Matters)
The rule is simple and non-negotiable: joints 1/8 inch or wider get sanded grout; narrower joints get unsanded. Getting it backwards is one of the most common — and most expensive to fix — tiling mistakes.
Why the sand matters
Sand adds structural bulk and resists shrinkage as the grout cures. In a wide joint, unsanded grout shrinks and cracks as it dries — there's nothing to hold the mass together. In a narrow joint, sanded grout's grit can scratch soft or polished surfaces and doesn't pack cleanly into tight spaces.
The one exception
Polished marble, polished granite, and other soft or glossy natural stone always get unsanded grout (or an epoxy formula) regardless of joint width — the sand permanently scratches the polished surface during application, no matter how careful you are.
Working with either
Sanded grout has a shorter working time and needs slightly more water control; unsanded is smoother to float but shows tool marks more readily. Our grout & thinset calculator makes the sanded-vs-unsanded call automatically based on the joint width you select, alongside the bag count.
Put it to work: every number in this guide comes straight from our free calculators — browse all 18 tools and get a shopping list for your own project.