Tile & Grout Calculator
Estimate tiles and grout needed for your project.
Installing tile is an art, but buying materials is a science. While most DIYers diligently calculate the square footage for tiles, the grout often becomes an afterthought—leading to panic runs to the hardware store mid-project with wet adhesive drying on the wall. The Tile Grout Calculator precisely estimates the amount of grout (in lbs or kg) required to fill the voids between your tiles based on dimensions and joint width.
Whether you are laying a subway tile backsplash, a large-format porcelain floor, or tiny mosaic sheets, getting the grout quantity right is essential for budgeting and ensuring color consistency across batches. Mixing bags from different manufacturing lots can lead to subtle color variations (shading) that ruin the look of your floor.
How to Use This Calculator
Accuracy depends on four key measurements. Grab your tape measure and specification sheet:
1. Tile Dimensions
Enter the exact size of the tile.
- Length & Width: E.g., 12″ x 24″. For square tiles, enter the same value twice.
- Thickness: This is crucial! A thicker tile (like 10mm stone) creates a deeper “canyon” to fill than a thin ceramic wall tile (6mm). Using a thicker tile effectively doubles the mass of grout needed.
2. Joint Width
This is the space between tiles, usually determined by your plastic spacers.
- 1/16″ or 1/8″: Common for rectified edges and modern, seamless looks.
- 3/16″ or 1/4″: Common for rustic tiles or irregular edges (like Saltillo or Travertine) to hide size variations.
3. Total Area
Enter the total square footage of the room. Don’t subtract the cabinets or island yet—it’s better to have a buffer than to run short.
Choosing the Right Grout Type
Not all grout is created equal. The type you choose dictates how much you need and how it will perform.
Sanded Grout
- Best For: Floors and wide joints (> 1/8 inch).
- Physics: It contains fine silica sand that adds structural strength, preventing the grout from shrinking and cracking in wide gaps. It locks the tiles together like mortar.
- Warning: DO NOT use on polished marble, glass, or metal tiles, as the sand can scratch the surface permanently.
Unsanded (Wall) Grout
- Best For: Walls, marble, glass, and tight joints (< 1/8 inch).
- Physics: It is a smooth paste made of Portland cement and powdered pigments. It is sticky, making it easy to cling to vertical surfaces without slumping.
- Warning: If used in a wide gap (> 1/8″), it will shrink as it cures, leading to unsightly cracks.
Epoxy Grout
- Best For: Showers, backsplashes, and high-traffic commercial areas.
- Physics: A two-part chemical reaction (Resin + Hardener). It is waterproof, stain-proof, and incredibly durable. It requires no sealing.
- Warning: It sets very quickly and is much harder to clean up during installation. It is also significantly more expensive.
Urethane / Pre-Mixed Grout
- Best For: DIYers who want convenience.
- Physics: These come in a bucket, ready to use. They offer good flexibility and stain resistance but can be tricky to clean off textured tiles if allowed to dry.
Common Grout Mistakes to Avoid
1. Adding Too Much Water
When mixing cement-based grout, adding too much water weakens the structure. The water evaporates, leaving behind air pockets (pinholes) and a powdery, weak joint that crumbles easily. Always follow the ratio on the bag.
2. Waiting Too Long to Wipe
Grout haze hardens rapidly. If you let it cure on the face of the tile, you may need acid to remove it, which can damage the tile finish. Begin wiping as soon as the grout effectively firms up in the joint.
3. Ignoring the Sealer
Standard cement grout is porous—it absorbs water, grease, and coffee spills like a sponge. Unless you used Epoxy, you MUST apply a penetrating sealer after the grout cures (usually 48-72 hours). This prevents stains and mildew growth.
The Math Behind the Mix
We use the Tile Council of North America (TCNA) standard formula for volumetric coverage.
Where:
- : Tile Length and Width
- : Tile Thickness
- : Joint Width
- : Grout Density (typically ~100 lbs/ft for powder)
Frequently Asked Questions (FAQ)
How much waste should I account for?
We recommend adding 10-15%. Grout gets spilled, wiped away on the sponge, and left in the bottom of the bucket. Ideally, you want to finish the entire room with one batch or one purchase to ensure the dye lots match.
Does tile shape matter?
Yes. Hexagons, Penny Rounds, and complex mosaics have significantly more “joint footage” per square foot than square tiles. Our calculator assumes rectangular/square tiles. For mosaics, assume 2-3x the standard grout amount calculated here.
Can I regrout over old grout?
Generally, no. You need to scrape out at least 2/3rds of the old grout depth to give the new grout something to mechanicaly bond to. A thin layer on top will just flake off. Use a carbide grout saw or an oscillating multi-tool for removal.
Why is my grout color lighter/darker than the sample?
Grout color is affected by drying time and water content. Too much water makes it lighter (efflorescence). Slow drying makes it harder and darker. Always do a test patch in a closet before committing to the center of the room.
Final Words
Don’t let a shortage of powder ruin your tiling day. The Tile Grout Calculator ensures you leave the store with exactly what you need to lock those tiles in place. Remember: Great tile work is 10% inspiration and 90% preparation—and having the right amount of grout is step one.
