How to Calculate Tile: A Complete Guide

Whether you are tiling a bathroom floor, a kitchen backsplash, or an entire living area, getting the quantity right saves time and money. Running out of tile mid-project is a real problem because tile lots vary in shade, and your exact lot may not be available for a reorder.

The Basic Tile Formula

Start with the total area, then divide by the coverage of each tile:

Number of Tiles = (Room Area + Waste Allowance) / Area per Tile

For example, a 10 ft x 12 ft bathroom floor using 12 x 12 inch tiles:

1. Room area: 120 sq ft
2. Waste at 10 percent: 12 sq ft
3. Total: 132 sq ft
4. Each 12 x 12 tile covers 1 sq ft
5. Tiles needed: 132

For smaller tiles, convert dimensions to feet first. A 6 x 6 inch tile covers 0.25 sq ft, so you would need 528 tiles for 132 sq ft. Tile is usually sold by the box — check the box label for square footage per box.

Choosing the Right Waste Factor

The waste factor depends on your layout pattern:

• Straight lay (grid): 10 percent for most rooms.
• Diagonal (45-degree): 15 percent due to more cuts along walls.
• Herringbone or chevron: 15 to 20 percent from numerous angled cuts.
• Large tile in a small room: 15 percent because oversized tiles generate more cut waste.

Keep a few spare tiles after the project for future repairs, since discontinued products are hard to match.

Grout and Thin-Set Estimates

• Thin-set mortar: A 50-pound bag covers 60 to 80 sq ft for standard tile with a 1/4-inch square-notch trowel.
• Grout: A 25-pound bag of unsanded grout covers about 200 sq ft of 12 x 12 tile with 1/16-inch joints, or about 70 sq ft with 1/4-inch joints.
• Use sanded grout for joints 1/8 inch and wider; unsanded for joints narrower than 1/8 inch.

When You Need This Calculator

• Homeowners retiling a bathroom who need tile counts plus grout and thin-set quantities. If you are renovating the full room, the Paint Calculator can help estimate wall paint at the same time.
• DIYers installing a backsplash who want quantities for a wall area with cutouts for outlets and windows.
• Contractors bidding a commercial floor job who need precise material counts for ordering and estimating.

Common Mistakes to Avoid

• Not subtracting fixed objects properly. Subtract vanities and built-in cabinets, but do not subtract toilets or appliances that sit on top of tile. If you are also replacing the walls, the Drywall Calculator helps you estimate sheets and finishing materials for the surrounding surfaces.
• Using too low a waste factor. Finding the same lot unavailable mid-project is common and frustrating. When in doubt, round up to 15 percent.
• Ordering from multiple lots. Color, size, and texture vary between production lots. Order all tile from the same lot number.
• Ignoring grout joint width. For small tiles with wide joints, grout area can be 10 to 15 percent of the floor, affecting both tile count and grout volume.

Pro Tips

• Dry-lay before you start. Set tiles without adhesive to plan cuts and adjust the starting point so edge tiles are at least half-width.
• Buy extra and keep the receipt. Most retailers accept returns on unopened boxes. Buy 15 percent extra, return what you do not use, and keep 3 to 4 spares.
• Use spacers for consistent joints. Common sizes are 1/16, 1/8, and 1/4 inch. Even experienced installers use them.
• Check tile flatness. Stack tiles face to face and edge to edge. If they rock or gap, they are warped and will be difficult to install flat.

Frequently Asked Questions

How many 12x12 tiles do I need for 100 square feet?

Each 12 x 12 inch tile covers 1 sq ft. You need 100 tiles plus waste: 110 tiles at 10 percent waste, or 115 for diagonal layouts. Check the tiles-per-box count on the packaging.

How much tile waste should I plan for?

Plan 10 percent for straight-lay in rectangular rooms, 15 percent for diagonal or complex shapes, and 20 percent for herringbone patterns.

What is the difference between wall tile and floor tile?

Floor tile must be harder to handle foot traffic — rated PEI 3 or higher for residential, PEI 4 to 5 for commercial. Wall tile can be thinner and lighter. Most floor tiles work on walls, but wall tiles should not be used on floors.