The amount of grout depends on how much joint there is: small tiles and wide, deep joints use far more grout than large tiles with narrow joints. Enter your tile size, joint size and the area to estimate how much grout to buy.
Formula
Grout (kg) = (L + W) ÷ (L × W) × J × D × Area × Density
L and W are the tile length and width, J the joint width and D the joint depth, all in millimetres; area in m² and density in kg/L. This is the formula grout manufacturers use on their coverage charts.
Worked example
300 × 300 mm tiles with 3 mm joints, 8 mm deep, over 10 m²: (600 ÷ 90,000) × 3 × 8 × 10 = 1.6 L. At 1.6 kg/L that is 2.56 kg, or about 2.8 kg with 10% extra.
Frequently asked questions
How much grout do I need per square foot?
For 12 × 12 in tiles with 1/8-inch joints 3/8 inch deep, roughly 0.07 lb per square foot. Smaller tiles such as mosaics need several times more.
Sanded or unsanded grout?
Unsanded grout is generally used for joints narrower than 1/8 inch (3 mm) and sanded grout for wider joints.
Last updated · Calculations checked by automated tests· Editorial policy