Grout Calculator

Estimate one tiled area

1. Choose Metric or US customary and enter tile face length and width, joint width, average filled joint depth and the installed area including joints. Use decimal inches, such as 0.125 for one eighth of an inch.
2. Enter the dry-powder coverage factor from the applicable product information. It is expressed as kilograms of powder per estimated liter of joint volume. Do not substitute loose-powder or mixed-mortar density.
3. Set a separate allowance if wanted and optionally enter the bag’s net powder weight. Read the approximate total and assumptions before using the rounded-up bag count.

What the estimate means

The approximate joint-volume method adds tile length and width, divides by their product, then multiplies by joint width and filled depth. With dimensions in millimeters, the result is numerically liters of joint volume per square meter.

Multiplying that volume equivalent by the product’s powder coverage factor gives kilograms of dry powder per square meter. ARDEX-FLEX FL’s referenced example uses 1.75; this is a product-specific method example, not a recommended factor for every grout.

Filled joint depth can differ from tile thickness. Bevels, adhesive in the joint, edge details and uneven filling affect the actual quantity. The formula approximates a regular tiled field and becomes less representative for wide joints or very small tiles.

Allowance is added before bag rounding. The bag count rounds the unrounded powder estimate upward, so a displayed total of 5.00 kg can require two 5 kg bags when the underlying estimate is slightly above 5 kg. This still does not guarantee site coverage.

Worked powder estimates

For 150 × 150 mm tiles, 5 mm joints, 5 mm filled depth and the example factor 1.75, the estimated rate is about 0.583 kg/m². Across 20 m² the base is about 11.67 kg. A 10% allowance gives about 12.83 kg, or two 10 kg bags.

For 300 × 600 mm tiles, 3 mm joints, 8 mm filled depth and an assumed factor of 1.6, the estimated rate is 0.192 kg/m². Across 20 m², adding 10% gives 4.224 kg before display rounding. One 5 kg bag exceeds that calculated amount. The assumed factor must be checked for the actual product.

A declared yield of 3.75 liters from 5 kg of powder corresponds to about 1.3333 kg of powder per liter. It is different from a mixed-grout density of 1.78 kg/L. Source figures may be rounded; use the product’s declared coverage or powder yield rather than treating wet mass as powder bags.

Approximation and product limits

This method estimates one uniform rectangular-tile field. It does not count exact edge joints, model mixed tile layouts, prescribe joint dimensions or check substrate, movement joints, waterproofing, installation suitability or local requirements. It excludes adhesive, movement-joint sealant, epoxy and ready-mixed grout.

Actual coverage varies with material yield, tile edges, surface conditions, filling, cleaning and waste. The allowance is your separate assumption, not a manufacturer recommendation. Regional product sheets can differ; confirm the applicable product instructions and use a test area when appropriate.

Calculated in your browser

The tool calculates from your entered dimensions and factor without tool-added uploads, saved project history or input-bearing links. Copy writes the current qualified summary to the clipboard only when requested. Normal site services and consent settings remain separate.