Grout Calculator
Work out how much grout you need in kg or lb from the tile size, tile thickness and joint width.
An estimate based on the joint volume and the grout density. Check the density and coverage on the data sheet of the grout you buy; uneven tile edges and leftover mix increase the amount used.
About this tool
Enter the area, the tile size, the tile thickness and the joint width. The calculator works out the joint volume per square metre (or square foot), multiplies it by the density of the grout and adds a waste allowance, so you know how many kilograms or pounds of grout — and how many bags — to buy. Works in metric (cm, mm, m²) and imperial (in, ft², lb).
Frequently asked questions
Use the joint volume: (tile length + tile width) × tile thickness × joint width × density ÷ ((length + joint) × (width + joint)), with all sizes in mm, gives kg per m². For 30 × 60 cm tiles, 9 mm thick, with 3 mm joints and a density of 1.6: 900 × 9 × 3 × 1.6 ÷ (603 × 303) = 0.21 kg/m². A 10 m² floor needs 2.13 kg, or 2.34 kg with 10% waste.
Check the data sheet of your grout. Cement-based grouts are typically around 1.5–1.9 kg per litre: ARDEX lists a fresh weight of about 1.70 kg/l for GF 3-1 K, ARDEX Endura uses 1.90 in its coverage formula, and 1.6 is a common middle value. A higher density means more kilograms for the same joints.
Smaller tiles mean more joints per square metre. With 3 mm joints, 60 × 60 cm tiles 10 mm thick need about 0.16 kg/m², while 10 × 20 cm tiles 8 mm thick need about 0.55 kg/m² — more than three times as much. Mosaic of 5 × 5 cm with 2 mm joints needs about 0.47 kg/m² even though the tiles are only 4 mm thick.
The formula only counts the joints themselves. Mix left in the bucket, uneven tile edges and grout wiped off the surface use more, so add around 10%. Grout is cheap compared with tiles, and having a little left over is useful for repairs later.
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