Tile Grout Bag Calculator
Calculate grout bags for any tile job from area, tile size, joint width, and tile thickness.
Works for floor, wall, and mosaic tile.
Grout volume scales with tile size, joint width, and tile thickness. Mosaic tiles need an order of magnitude more grout per square foot than 12-inch floor tiles, and a half-inch saltillo joint can need ten times more grout than a sixteenth-inch porcelain joint at the same tile size.
What the math computes is pounds of grout per square foot of floor:
pounds_per_sqft = 24 × joint_width ÷ tile_size × (tile_thickness ÷ 0.375)
Sizes in inches. The constant is calibrated against the coverage charts printed on the bags, so a 12-inch tile with 1/8-inch joints at standard 3/8-inch thickness comes out at 0.25 lb per sq ft, which is 100 sq ft from a 25 lb bag.
Mosaic flips the result hard. Drop the tile to 1 inch and the same formula gives 1.5 lb per sq ft at a 1/16-inch joint, or about 17 sq ft per bag. Six times the grout for the same floor, because grout tracks total joint length and small tile means far more of it. A mosaic shower pan can quietly eat more grout than the entire bathroom floor around it.
The bag math. A standard 25 lb bag of sanded grout (the common floor grout) covers roughly 50 to 100 sq ft for typical tile depending on size and joint, and 15 to 20 sq ft for mosaic, which is exactly what the formula above reproduces. Unsanded grout (for joints under 1/8 inch) is denser and covers slightly less area per pound. Premixed grout in a bucket covers about 60 percent of what the same weight in dry mix would, but you skip the mixing.
Always buy one extra bag past whatever the calculator says, especially for premixed colors. Grout color slightly varies between batches, and finishing a job with a separate run of grout will leave a visible line on the last few rows. Bringing back unopened bags is easier than driving to Home Depot at 8 PM with three feet left to grout.
A practical detail. Bullnose, decorative borders, and edge tile have more perimeter per sq ft than flat fields, so a job with a lot of detail uses more grout than a featureless floor of the same area. The calculator rounds up generously, but for ornate jobs add a 20 percent margin on top.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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