What is Tile Grout?
Tile grout is a material used to fill the gaps between tiles to prevent dirt, moisture, and liquids from penetrating underneath. When installing tiles, small gaps are left between each tile to accommodate future thermal expansion, structural movement, and to prevent cracking or lifting. Grout fills these gaps, adds to the aesthetics of the tiled surface, and protects the substrate beneath.
Grout is generally a composite material made from a mixture of cement, lime, and water, and may also contain sand — similar to concrete and mortar. There are several types of grout:
- Sanded grout — contains fine sand; recommended for joints wider than 1/8 inch (3 mm). Ideal for floors and large tile installations.
- Unsanded grout — smoother texture; best for joints narrower than 1/8 inch (3 mm) or for polished stone tiles where sand may cause scratches.
- Epoxy grout — made from epoxy resins and hardener; highly resistant to chemicals, stains, and moisture. Used in kitchens, bathrooms, and commercial spaces.
- Furan grout — similar to epoxy but even more chemical-resistant; used in industrial environments.
How to Calculate Cement Grout Volume
To calculate the volume of grout needed, you need to determine the total volume of the gaps between the tiles. Our calculator uses the ratio R of the area of a single tile to the area of a single tile including half of the surrounding grout joint:
- R = (tile length × tile width) / ((tile length + joint width) × (tile width + joint width))
- Gap fraction = 1 − R — proportion of the floor area occupied by grout joints
- Gap area = total room area × gap fraction
- Grout volume = gap area × grout depth (tile thickness)
- Add wastage allowance (typically 10%) for cuts and losses
The weight of grout is then calculated using the density of dry cement grout (approximately 1.5 g/cm³ or 93 lb/ft³), and the number of bags required is determined by dividing the total weight by the bag size.
How to Use Our Grout Calculator
- Choose your unit system — Imperial (ft/in) or Metric (m/cm/mm)
- Enter room dimensions — length and width of the area to be tiled
- Enter tile dimensions — length and width of a single tile
- Specify grout joint width — the width of the gap between tiles (typically 1/8 in or 3 mm)
- Specify grout depth — equal to tile thickness (typically 1/4 in or 6 mm)
- Set wastage percentage — add 10% for standard projects, 15% for complex layouts
- Enter bag size and price — to get the number of bags and total cost in your preferred currency
- Click Calculate to get your results instantly
Tips for Grouting
- Always buy 10–15% more grout than calculated to account for waste and future repairs
- Choose sanded grout for joints wider than 1/8 inch; use unsanded grout for narrow joints or polished stone
- Mix grout to a smooth, peanut-butter consistency and let it slake for 5–10 minutes before applying
- Apply grout diagonally across the tiles using a rubber grout float
- Clean excess grout within 20–30 minutes with a damp sponge before it fully cures
- Seal grout lines after curing (24–72 hours) to prevent staining and moisture penetration
- Color-match your grout to the tile for a seamless look, or choose a contrasting color to highlight the pattern
Frequently Asked Questions
How much grout do I need per square foot?
The amount of grout depends on tile size and joint width. For a 12×12 inch tile with a 1/8 inch joint, you typically need about 0.5–0.7 lb of grout per square foot. Smaller tiles or wider joints require significantly more grout. Use our calculator for an accurate estimate for your specific project.
What is the standard grout joint width?
Standard grout joint widths are:
- 1/16 inch (1.5 mm) — rectified tiles with very tight tolerances
- 1/8 inch (3 mm) — most common for wall and floor tiles
- 3/16 inch (5 mm) — larger tiles or irregular stone
- 1/4 inch (6 mm) — rustic or handmade tiles with natural variation
How long does grout take to dry?
Cement grout typically takes 24–72 hours to cure before light foot traffic, and 7–14 days to fully cure. Epoxy grout may cure faster (12–24 hours). Always follow the manufacturer's instructions and avoid moisture during curing.
How do I know if I need sanded or unsanded grout?
Use unsanded grout for joints under 1/8 inch (3 mm) or for polished stone like marble that could be scratched by sand. Use sanded grout for joints 1/8 inch (3 mm) and wider, especially for floors or textured tiles.
Can I use this calculator for shower tile grout?
Yes. Enter the total tiled area of your shower walls and floor, along with tile size and joint width, and the calculator will give you the grout quantity. For showers, consider using epoxy grout or a high-quality cement grout sealer for superior water resistance.