Grout Calculator
Grout fills only the joints, so small tiles need far more grout than large ones for the same floor. Enter your tile and joint to get the grout weight and bag count. Runs 100% in your browser.
Grout Calculator
About this grout calculator
Grout weight follows the joints, not the tiles: joint share = 1 − (tile length ÷ (tile length + joint)) × (tile width ÷ (tile width + joint)), then pounds = area × joint share × joint depth in feet × grout density (about 120 lb per cubic foot sanded, 105 unsanded). A 100 sq ft floor of 12×12 tiles with 1/8-inch joints at 3/8-inch depth needs about 7.69 lb net, 8.46 lb with 10% waste — one 25 lb bag. The same floor in 6×6 tiles needs about 15.15 lb net, 16.66 lb with waste — smaller tiles mean more joints per square foot, and joints are the only place grout goes. Our grout guide works through the same math with a coverage table.
Sanded vs unsanded is decided by the joint, not by preference: sanded grout for joints 1/8 inch and wider, where the sand stops wide joints shrinking and cracking; unsanded for joints under 1/8 inch and for polished stone, glass, and metal tile, where sand can scratch the surface. Epoxy grout is a third option — stain-proof and waterproof, but harder to work and priced per kit rather than per pound, so this calculator's bag count does not apply to it.
The depth you enter is the grout thickness in the joint, usually close to the tile thickness — floor tiles are often 3/8 inch thick, wall tiles 1/4 to 5/16 inch. If you are regrouting over old grout rather than grouting fresh tile, measure the depth of the joint you are actually filling, not the full tile thickness, or you will overbuy.
How to use
- Measure the tile area in square feet (length × width of the tiled surface).
- Enter the tile length and width in inches, and the joint width in inches (1/8 inch = 0.125).
- Enter the joint depth in inches — usually the tile thickness.
- Choose sanded or unsanded grout and a waste allowance (10% covers what stays on the float).
- Press Calculate for the grout weight and bag count.
Good to know
- Rectangular tiles and uniform joints only. Mosaic sheets, hexagons, and pebble tile have different joint patterns and need the manufacturer's coverage chart.
- Density is an estimate (120 lb/cu ft sanded, 105 unsanded) — brands vary. Always check the coverage printed on the bag you buy and go with the bag if it disagrees.
- Does not cover epoxy grout (sold by kit, not by weight) or grout for movement joints and expansion joints, which use sealant, not grout.
Frequently asked questions
How much grout do I need for 100 square feet of tile?
For 12×12 tiles with 1/8-inch joints at 3/8-inch depth, about 7.69 lb net — 8.46 lb with 10% waste, so one 25 lb bag. For 6×6 tiles at the same joint, about 15.15 lb net, 16.66 lb with waste.
Should I use sanded or unsanded grout?
Sanded for joints 1/8 inch and wider; unsanded for joints under 1/8 inch and for polished stone, glass, or metal tile that sand could scratch.
How is grout coverage calculated?
From the joint share of the surface: 1 minus (tile length × tile width) divided by ((length + joint) × (width + joint)), times the area, times the joint depth, times the grout density — then waste, then round up to whole bags.
Does tile size really change how much grout I need?
More than any other input. At 1/8-inch joints and 3/8-inch depth, grout per 100 sq ft runs from about 3.88 lb on 24×24 tiles to 15.15 lb on 6×6 tiles and over 22 lb on 3×6 subway tiles.
What waste percentage should I add for grout?
10% is the standard allowance for what stays on the float, in the bucket, and in sponge water. Use 15% for mosaics and jobs with many cuts.