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Grout Calculator: How Much Grout Do I Need?
Estimate pounds and bags of grout for any tile size, tile thickness and joint width. Small mosaic tiles need several times more grout than large format tile, and this calculator shows exactly how much.
How grout is calculated
Grout fills the joints between tiles, so the amount depends on how many feet of joint there are and how big each joint is. The volume of grout per square foot is:
grout (cu in per sq ft) = 144 × (L × J + W × J + J²) × T ÷ ((L + J) × (W + J))
where L and W are the tile length and width, J is the joint width and T is the tile thickness, all in inches. Mixed cement grout weighs about 0.065 lb per cubic inch, and the calculator adds 10% for mixing loss and cleanup.
Worked examples
- 12 × 12 in floor tile, ⅜ in thick, ⅛ in joints: about 1.1 cu in of grout per sq ft, or 7.2 lb per 100 sq ft. A 25 lb bag covers roughly 310 sq ft.
- 2 × 2 in mosaic, ¼ in thick, ⅛ in joints: about 4.1 cu in per sq ft, or 27 lb per 100 sq ft. The same 25 lb bag covers only about 85 sq ft.
- 12 × 24 in porcelain, ⅜ in thick, 1/16 in joints: about 0.4 cu in per sq ft, so a 10 lb bag covers around 330 sq ft.
Sanded or unsanded grout?
| Joint width | Grout type | Typical use |
|---|---|---|
| 1/16 in to under ⅛ in | Unsanded | Polished stone, glass tile, rectified porcelain, walls |
| ⅛ in to ½ in | Sanded | Most ceramic and porcelain floors, showers |
| Any width, wet or stain-prone areas | Epoxy or urethane | Showers, kitchen backsplashes, commercial floors |
Do not use sanded grout on soft polished marble or glass: the sand can scratch the surface as you work it in. Premixed urethane and epoxy grouts are sold by volume (pails), so convert using the coverage chart on the pail.
Tips
- Mix only what you can use in about 30 minutes. Grout that has started to stiffen should not be re-tempered with more water.
- Buy all bags from one lot so the color matches, and keep a little for future repairs.
- Wait for the thinset to cure (usually 24 hours) before grouting. See our tile calculator for tile count and thinset.
Frequently asked questions
How much grout do I need for 100 square feet?
For 12 × 12 in tile, ⅜ in thick, with ⅛ in joints, you need about 7 to 8 lb, so one 10 lb bag. Small mosaic tile needs much more: about 27 lb per 100 sq ft for 2 × 2 in tile.
How many square feet does a 25 lb bag of grout cover?
It depends on the tile. With 12 × 12 in tile and ⅛ in joints a 25 lb bag covers about 300 sq ft; with 1 × 1 in mosaics only about 50 sq ft.
When should I use sanded grout?
Use sanded grout for joints ⅛ in wide and wider, and unsanded grout for narrower joints and for polished stone or glass tile that sand could scratch.