How much grout do I need for a tile job?

It comes from the joints, not the tiles: the smaller the tile, the more joint per square foot, and a wider or deeper joint fills faster. This tool takes your tile size, joint width and tile thickness, works out the volume of grout per unit of area, multiplies by the floor or wall area and turns it into a weight and a bag count.

Why does small tile use so much more grout?

A mosaic has a joint around every little tile, so there is far more total joint length in a square foot than there is with a large-format tile. Because the grout volume tracks that joint length, halving the tile size roughly doubles the grout. The formula shows it directly — the tile dimensions sit in the denominator.

What density and bag size should I enter?

Both are on the product. Mixed grout is roughly 90 pounds per cubic foot, near 1440 kilograms per cubic metre, and those are the editable defaults — a sanded grout runs a little heavier. Bags are commonly 25 pounds or about 11 kilograms. Use the figures from the bag in front of you for the closest count.

Grout calculator

This estimates grout from clean joint geometry and a density you set. Real coverage shifts with mixing, how full you pack the joints and the trowel work, so it runs generous on purpose — round up, and mix a full bag rather than stopping a job to open another.

Enter the tiled area, the tile size, the joint width and the tile thickness. The tool finds the grout volume per unit of area from the joint geometry, multiplies by the area, then turns that volume into a weight and a bag count using the density and bag size you enter.

Worked example

A 10 ft × 10 ft floor is 100 sq ft in 12-inch tiles, 5/16 inch thick, with a 3/16 inch joint. The grout per square foot works out to a thin film — about 0.0008 ft³ — so the floor takes roughly 0.08 ft³ of grout, near 7 lb, comfortably inside one 25 lb bag. Switch to 2-inch mosaic and the same floor jumps past a full bag.

The formula

grout per area = ((tile L + tile W) ÷ (tile L × tile W)) × joint width × thickness

With the tile dimensions in the joint's own length unit, that expression has units of length — it is the grout volume for each unit of tiled area. Multiply by the area to get a volume, by the density for a weight, and divide by the bag size for the count. The tile size in the denominator is why mosaics drink grout.

Questions

How much grout do I need for a tile job?: It comes from the joints, not the tiles: the smaller the tile, the more joint per square foot, and a wider or deeper joint fills faster. This tool takes your tile size, joint width and tile thickness, works out the volume of grout per unit of area, multiplies by the floor or wall area and turns it into a weight and a bag count.
Why does small tile use so much more grout?: A mosaic has a joint around every little tile, so there is far more total joint length in a square foot than there is with a large-format tile. Because the grout volume tracks that joint length, halving the tile size roughly doubles the grout. The formula shows it directly — the tile dimensions sit in the denominator.
What density and bag size should I enter?: Both are on the product. Mixed grout is roughly 90 pounds per cubic foot, near 1440 kilograms per cubic metre, and those are the editable defaults — a sanded grout runs a little heavier. Bags are commonly 25 pounds or about 11 kilograms. Use the figures from the bag in front of you for the closest count.

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