How much grout do I need?
Grout doesn't cover an area the way paint or thinset does — it fills the joints between tiles. So the amount you need depends on how much joint there is, which comes down to four things: tile length, tile width, tile thickness, and joint width. The standard estimate is:
Pounds per sq ft = ((tile L + tile W) ÷ (tile L × tile W)) × joint width × tile thickness × 14.5
(All tile dimensions in inches.) Multiply by your tiled area, then divide by the bag size and round up. The takeaways: smaller tiles have more joint per square foot — a mosaic uses several times the grout of a big tile — and wider or deeper joints use proportionally more. That's why this calculator asks for tile and joint sizes instead of just area.
What drives grout coverage
Here's how far a single 25 lb bag of sanded grout stretches for some common setups. Notice how much tile size and joint width change the answer.
| Tile & joint | Grout per 100 sq ft | 25 lb bag covers |
|---|---|---|
| 2×2″ mosaic, 1/8″ joint | ~45 lbs | ~55 sq ft |
| 3×6″ subway, 1/16″ joint | ~14 lbs | ~175 sq ft |
| 12×12″ floor, 1/8″ joint | ~11 lbs | ~220 sq ft |
| 12×12″ floor, 1/4″ joint | ~23 lbs | ~110 sq ft |
| 18×18″ floor, 3/16″ joint | ~11 lbs | ~220 sq ft |
Assumes 3/8″ tile thickness (5/16″ for subway, 1/4″ for mosaic). Your bag may differ — match the price and bag size to what you buy.
Sanded vs. unsanded vs. epoxy
- Unsanded grout — for narrow joints up to 1/8″ and for polished or scratch-prone tile like glass, metal, and polished stone.
- Sanded grout — for joints 1/8″ and wider. The sand resists shrinking and cracking, and it's the standard for floors.
- Epoxy grout — stain-proof and waterproof, ideal for kitchens, showers, and heavy use. It's pricier, sets fast, and is estimated by its own kit coverage.
Tips for grouting tile
- Let the thinset cure first. Wait at least 24 hours after setting tile before you grout, so the mortar isn't still wet under the tile.
- Mix small batches. Grout starts setting in the bucket — mix what you can spread and clean in about 30 minutes, and don't add water to revive it.
- Pack joints full. Work the float diagonally across the tile to force grout in with no gaps or low spots, then tool the joints consistently.
- Seal cement grout. After it cures (48–72 hours), seal sanded and unsanded grout to fight stains, and reseal every year or two in wet areas.