Sanded vs Unsanded Grout
The 1/8 in joint is the dividing line: sanded grout for joints at or above that threshold, unsanded for below. Here is why — and the live grout calculator to estimate both.
The 1/8 in rule
The tile industry's standard threshold is 1/8 in (3 mm):
- Joint < 1/8 in → Unsanded grout (smooth paste, no aggregate, lower density ~90 lb/ft³). Used for polished marble, glass, and narrow-joint ceramic.
- Joint ≥ 1/8 in → Sanded grout (silica sand aggregate resists shrinkage in wider joints, density ~104 lb/ft³). Used for most floor and wall tile.
The sand in sanded grout fills the joint volume more efficiently and resists the shrinkage cracks that appear in wider, unsanded joints. In joints under 1/16 in the sand particles physically will not fit.
When to use epoxy grout
Epoxy grout (density ~110 lb/ft³) is appropriate when you need:
- Chemical resistance (kitchen counters, commercial food prep)
- Stain resistance without a separate sealer
- Moisture-rich environments (pool decks, steam showers)
Epoxy is more expensive and more difficult to apply than cement-based grout. It has a limited working time and must be mixed in exact ratios. For most residential applications, a quality polymer-modified cement grout with a penetrating sealer is sufficient.
Does the type change how much grout I need?
Yes — because density differs. Per cubic inch of joint volume: sanded grout weighs 104/1728 = 0.0602 lb/in³; unsanded weighs 90/1728 = 0.0521 lb/in³ — about 15% lighter. For the same joint geometry you order slightly more pounds of sanded grout. The calculator below applies the correct density automatically.
Calculate grout for your tile job
Tile & Area
Grout Joint
Grout Type & Bag Size
How the grout formula works
Step 1 — joint length per unit area (TCNA/Laticrete geometry)
joint_len_per_area = (tile_L + tile_W) / (tile_L × tile_W) [1/in] Each tile shares half its perimeter with its neighbours, netting (L+W) of joint per tile face area L×W. A 12×12 yields 24/144 = 0.167/in; a 2×2 mosaic yields 4/4 = 1.0/in — 6× more grout for the same area.
Step 2 — grout weight per square foot
lb/sq ft = joint_len_per_area × joint_width × joint_depth × density (lb/in³) × 144 Density: sanded 104 lb/ft³ (= 0.0602 lb/in³), unsanded 90 (= 0.0521), epoxy 110 (= 0.0637). Multiplying by 144 in²/ft² converts the per-in² result to per-ft².
Step 3 — total pounds and bags
grout_lb = lb/sq ft × area × (1 + waste%/100) bags = ⌈ grout_lb / bag_size − 1e−9 ⌉ The −1e−9 float guard prevents a spurious extra bag when the result lands on exactly a whole number due to floating-point rounding.
Related tools
Frequently Asked Questions
Sanded grout contains silica sand as an aggregate. The sand reduces shrinkage as the grout cures, making it structurally stronger in wider joints (1/8 in and wider). Unsanded grout is a smoother paste used in narrow joints under 1/8 in — or wherever sand would scratch the tile surface. Sanded grout is denser: about 104 lb/ft³ vs 90 lb/ft³ for unsanded.
Not in joints under 1/16 in — the sand particles will not fit. For joints between 1/16 in and 1/8 in it is possible but not recommended: the sand can damage polished tile (marble, glass) and the slightly coarser texture makes cleanup harder in tight joints. The 1/8 in line is the generally accepted threshold.
Yes. Without the sand aggregate to control shrinkage, unsanded grout in joints wider than 1/8 in will typically crack as it dries. Some premium unsanded grout products (fine-unsanded formulas) allow slightly wider joints — check the bag specifications. For joints 1/8 in and wider, sanded grout is the reliable choice.
Yes, because density differs. Sanded grout (104 lb/ft³) is denser than unsanded (90 lb/ft³) — so for the same joint geometry you need slightly more by weight of sanded grout. The calculator adjusts the estimate automatically when you select grout type. The difference is about 15% by weight for the same volume of joint.
Epoxy grout is a two-part system (resin + hardener) that does not use Portland cement. It is denser (about 110 lb/ft³), chemically resistant, and stain-resistant without a separate sealer. It is the correct choice for food-service areas, chemical exposure, or wet commercial environments. Epoxy is harder to apply and more expensive than cement-based grout — follow the manufacturer's mixing instructions precisely.