Grout Calculator
How much grout a tiled floor or wall needs from the area, the tile size, and the width and depth of the joints — in kilograms and bags.
Grout fills the joints, so the volume is the joint length per square meter × joint width × joint depth.
How the grout calculator works
Grout fills the joints, so the volume is the joint length per square meter × joint width × joint depth. A square meter of tiles of length L and width W has about (L + W) ÷ (L × W) meters of joint per square meter; multiply by the joint width and the tile thickness (the depth), then by the grout’s density — about 1.6 kg per liter of filled joint for cement grout — and add 10% for waste.
Formula: kg = area × (L + W) ÷ (L × W) × joint width × depth × 1.6 kg/L × 1.1
Worked examples
| Inputs | Grout to buy | Note |
|---|---|---|
| 12 m² of 600 × 300 tiles, 3 mm joints, 10 mm deep | 1 × 5 kg bag | 3.2 kg — one 5 kg bag |
| 130 sq ft of 12 × 12 in tiles, ⅛ in joints | 1 × 4.5 kg bag | about 1.4 kg |
| Mosaic: 4 m² of 50 × 50 mm, 2 mm joints, 6 mm deep | 1 × 5 kg bag | 3.4 kg |
FAQFrequently asked questions
Why does tile size matter so much?
Small tiles have far more joint per square meter: 100 mm mosaics need about six times the grout of 600 mm tiles at the same joint width. The formula counts the joint length, which is what drives it.
What depth should I use?
The tile thickness — grout should fill the joint to the tile’s full depth. Porcelain floor tiles are 8–10 mm; wall tiles 6–8 mm; natural stone can be 12–20 mm.
Sanded or unsanded?
Sanded grout for joints over about 3 mm, unsanded for narrow joints and polished tiles it could scratch. Epoxy grout is denser (about 1.8 kg/L) and comes in smaller packs — adjust the density in your head or buy 10% more.
How much waste should I allow?
The 10% built in covers grout left in the bucket and joints slightly wider than planned. Rectified tiles laid tight need less; hand-made tiles with irregular edges need more.
Where these figures come from
- The Engineering ToolBox — material densities, coverage and unit data — bulk densities, concrete at 2,400 kg/m³, board and sheet sizes
- Gypsum Association — gypsum board sizes — 4 × 8 and 4 × 12 ft sheets
- ADA Standards for Accessible Design — ramps (§405) — maximum running slope 1:12
- International Code Council — the International Residential Code
Last checked: September 2026. Coverage rates and material sizes are typical manufacturer figures — check the product you buy.