Home & Construction
How much grout does your tile job need? Enter the tile size, the area, and the joint width and depth for an estimate in pounds and bags. This is a planning estimate — always check the coverage chart on your grout bag before you buy.
Grout only goes in the joints, so the calculator measures the total joint volume. Each tile accounts for one lengthwise and one widthwise run of joint, so the joint volume per tile is (tile length + tile width) × joint width × joint depth, in cubic inches. Multiplying by how many tiles fit in your area gives the total volume to fill.
Dry grout weight comes from the yield: how many cubic inches of filled joint one pound of dry grout produces once mixed. The default of 12 cu in/lb is a mid-range figure for cement grouts — it puts a 10 lb bag at roughly 100 sq ft on 12×12 tile with ⅛″ joints, in line with typical manufacturer coverage charts. Different products vary (sanded vs. unsanded, single-component and epoxy grouts), so if your bag lists a yield or coverage for your tile and joint size, adjust the yield input to match it. Joint width is the big lever: doubling the joint width roughly doubles the grout.
Joint depth should be the depth grout actually fills — usually the tile thickness, and often a bit less on cushioned or beveled-edge tile. Common joint widths: 1/16″ (0.0625) for rectified tile, ⅛″ (0.125) standard, 3/16″ (0.1875), and ¼″ (0.25) for rustic or stone tile. The waste allowance (10% by default) covers mixing loss, the grout that washes off during cleanup, and joints that run deeper than planned.
Why does the store's coverage chart disagree? Charts assume a specific yield and a perfectly uniform joint depth. Real installations vary — treat this result and the chart as two estimates of the same job, and buy for the higher one if the price difference is small. Running out mid-job is worse than a spare bag.
Does tile shape change the math? The formula assumes rectangular tile in a straight grid. Small mosaics have far more joint per square foot (enter the individual tile size, not the sheet size), and patterns like herringbone or brick-laid add joints, so round up an extra bag.
Sanded or unsanded grout? A material choice, not a math one: unsanded is typical for joints under ⅛″ and delicate glazed tile, sanded for wider joints. Their yields are close enough that the same estimate covers both, but verify against your product's chart.
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