Grout Calculator

Enter the length and width of the area you are tiling, pick your tile size, and choose your joint (grout line) width — that is all it takes to get an estimate. The calculator instantly returns how many pounds of grout you need and how many bags to buy. Open More options to switch to metric, set the joint depth (tile thickness), change the bag size, or add a price per bag to see total cost. Everyone asks the same thing: *how much grout do I need for a 12x12 tile floor?* This tool answers it in one screen.

Grout fills the lines *between* tiles, so the amount you need is driven by three things: the tile size, the joint width, and the joint depth. Small tiles and wide joints mean more linear grout line per square foot, so you use more grout. Large-format tiles with a thin 1/16 in joint use very little. This is why a mosaic wall can burn through several bags while a 24x24 floor of the same size barely needs one. The calculator works out the total length of grout line packed into your square footage, multiplies by the joint's cross-section, and converts that volume to pounds and bags.

Grout volume per sq ft (in³) = ((tileL + tileW) ÷ (tileL × tileW)) × jointWidth × jointDepth × 144

Multiply by your total square footage for total volume, divide by 1,728 to get cubic feet, then multiply by grout density (≈125 lb/ft³) to get pounds. Bags = pounds ÷ bag weight, rounded up to whole bags. All tile and joint dimensions are in inches; area is in square feet.

Example 1 — a 20 x 20 ft floor, 12x12 tile, 1/8 in joints: Area = 400 sq ft. Grout volume per sq ft = ((12+12)÷144) × 0.125 × 0.375 × 144 = 1.125 in³. Total = 450 in³ = 0.26 ft³ × 125 = 32.6 lb, so buy 2 × 25 lb bags.

Example 2 — a small 5 x 8 ft subway backsplash, 3x6 tile, 1/16 in joints: Area = 40 sq ft. Per sq ft = ((3+6)÷18) × 0.0625 × 0.375 × 144 = 1.687 in³. Total = 67.5 in³ = 0.039 ft³ × 125 = 4.9 lb, so 1 bag easily covers it.

- Always round up to whole bags — you cannot buy a partial bag, and running out mid-job means a color-match nightmare with a fresh bag.
- Buy one extra bag for large jobs. Grout mixed at different times can shade slightly differently, so having spare from the same lot is cheap insurance.
- Match grout type to joint width: use *sanded* grout for joints 1/8 in and wider, *unsanded* for 1/16 in and thinner. Sanded grout is denser and covers a touch less.
- Joint depth ≈ tile thickness. Thicker tiles (like 3/8 in porcelain) hold more grout than thin 1/4 in wall tile — set it under More options for a tighter estimate.
- Manufacturer coverage charts vary; treat this as a solid planning estimate, not a guarantee.