How much grout do I need?

Grout quantity depends on how much empty space the joints create, not on the floor area alone. Smaller tiles mean more joints per square foot, wider joints mean more volume in each, and thicker tile means the joint is deeper. That is why a 100 sq ft floor of 12 inch tiles needs about 7 lb of grout while the same floor in 6 inch tiles needs almost exactly twice as much.

Tiled area (sq ft)

Tile length (in)

Tile width (in)

Joint width (in)

1/8 in is standard; 1/16 in for rectified porcelain.

Tile thickness (in)

Grout needed

7.3lb

Grout in kg 3.32 kgJoint volume 113 in³

An estimate for cementitious grout at flush joints. Deep joints, bevel-edged tiles and epoxy grout need the manufacturer's coverage chart.

The calculation estimates the joint volume geometrically: for each square foot, the linear inches of joint multiplied by the joint width and the tile thickness. Grout powder is then converted by density — about 0.065 lb per cubic inch, or roughly 1.8 g/cm³ for a cementitious grout once mixed.

Two practical points the number does not show. Grout is sold in 10 lb and 25 lb bags at most suppliers, so 7.3 lb means buying a 10 lb bag. And epoxy grout is denser and sold by volume with different coverage, so use the manufacturer's chart rather than this figure if you are using epoxy.

How the calculation works

Joint volume (in³) = area (sq ft) × 144 × ((tile length + tile width) ÷ (tile length × tile width)) × joint width × tile thickness. Weight = volume × 0.065 lb/in³.

The fraction (L + W) ÷ (L × W) is the linear inches of joint per square inch of tile face — it rises sharply as tiles get smaller, which is the whole reason tile size dominates grout consumption.

• Cementitious grout at about 1.8 g/cm³, equivalent to 0.065 lb per cubic inch once mixed.
• The joint is filled flush and to the full tile thickness; a grout that is not packed to the bottom uses less, and a deep bevel uses more.
• No allowance is added for waste, because grout is mixed in batches and leftover powder keeps; the bag size is the practical constraint.
• Sanded versus unsanded affects handling, not the volume figure.

Sources: Cementitious grout density: ~1.8 g/cm³ = 0.065 lb/in³; Joint linear inches per sq ft = 144 x (L + W) / (L x W) for tile dimensions in inches

Worked examples

Questions

How much grout do I need per square foot?

About 0.07 lb per sq ft for 12 x 12 tile with 1/8 in joints, and about 0.15 lb for 6 x 6 tile. Smaller tiles use proportionally more.

How many square feet does a 10 lb bag of grout cover?

Roughly 130 sq ft for 12 x 12 tile with 1/8 in joints, and about 65 sq ft for 6 x 6 tile. Wider joints reduce either figure.

Does wider joint spacing use more grout?

Yes, in direct proportion. Doubling the joint width doubles the grout for the same tile size.

What about epoxy grout?

Epoxy is sold by volume with its own coverage chart, and it does not shrink. Use the manufacturer's figure — this calculator is calibrated for cementitious grout.

Should I add a waste allowance for grout?

Not much. Buy the next bag size up rather than adding a percentage, since mixed grout cannot be stored and dry powder keeps indefinitely.

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Written and maintained by Sam Winters. Last updated 2026-11-04. Every figure is computed in your browser; nothing you enter is sent anywhere. Found an error? Tell me — accuracy reports get fixed first.