How Many Floor Tiles Do I Need?
Tile math is refreshingly simple. Convert your tile size to square feet (a 12 by 12 tile is exactly 1 square foot; a 24 by 24 is 4), divide the room area by that number, and add your waste allowance:
Tiles = ceiling(floor area / tile area x (1 + waste %))
For an L-shaped room, break it into two rectangles, calculate each, and add them. Then convert tiles to boxes: divide by the tiles per box on your carton and round up. Most porcelain floor tiles come 4 to 9 per box depending on size. Measure in centimeters? Convert to inches first with our unit converter, since US tile is sold in inches.
Grout Calculator: How Much Grout Per 100 Sq Ft
Grout fills the joints between tiles, and the amount depends on tile size, joint width, and joint depth. The industry formula (used by manufacturers like Custom Building Products) is: grout pounds = (tile length + tile width) x joint width x joint depth x 144 / (tile length x tile width) x floor area / 1728. Our calculator applies it automatically. As a quick reference for 25 lb bags:
| Tile size | Joint width | Grout per 100 sq ft |
| 12 x 12 in | 1/16 in | 0.4 to 0.6 bags |
| 12 x 12 in | 1/8 in | 0.5 to 0.7 bags |
| 18 x 18 in | 1/8 in | 0.6 to 0.8 bags |
| 24 x 24 in | 1/8 in | 0.7 to 1 bag |
| 6 x 6 in | 1/8 in | 0.3 to 0.4 bags |
Smaller tiles mean more grout lines per square foot, so they drink more grout. Unsanded grout suits joints up to 1/8 inch; sanded grout handles 1/8 inch and wider without shrinking or cracking. Need the exact percentage bump for a wide joint? Check it with our percentage calculator.
Thinset Mortar: How Much Do You Need?
Thinset is the adhesive bed under the tile, and coverage depends on your trowel notch. Bigger tiles need a bigger notch so the mortar fully supports them:
| Trowel notch | For tile sizes | Coverage per 50 lb bag |
| 3/16 in V-notch | Mosaics, up to 6 in | 60 to 70 sq ft |
| 1/4 x 1/4 in square | 6 to 12 in | 50 to 60 sq ft |
| 1/4 x 3/8 in square | 12 to 18 in | 40 to 50 sq ft |
| 1/2 x 1/2 in square | 18 in and larger | 30 to 40 sq ft |
For large-format tiles (any side 15 inches or more), back-butter each tile, spreading a skim coat on the back, to hit the 80% mortar coverage the Tile Council of North America (TCNA) requires. If your subfloor is uneven, level it first; estimate the leveling material with our concrete calculator.
Tile Layout Patterns and Waste
The pattern changes both the look and the number of tiles you buy. A straight grid is the most economical: cuts only happen at the walls, and offcuts often start the next row. A diagonal layout at 45 degrees wastes 10 to 15% more because every edge tile needs an angled cut. Herringbone and chevron waste 15 to 20% and take considerably longer to install, which shows up in labor quotes. Whatever pattern you choose, buy from the same dye lot: the shade number is printed on every box, and lots can differ just enough to show.
Popular Tile Sizes and Where They Work Best
Porcelain dominates US floor tile sales from brands like Daltile and MSI because it is dense, low-absorption, and hard to stain. Ceramic costs less but chips more easily. For small bathrooms and kitchens, 12 by 12 remains the practical sweet spot: enough tiles to keep cuts simple, small enough to slope toward a shower drain. Large-format 24 by 24 porcelain makes open living areas feel bigger with fewer grout lines, but it demands a flat subfloor and costs more per square foot to install. Wood-look planks (typically 6 by 24 or 8 by 36) give you the hardwood look with tile durability, and rectified edges allow tight 1/16 inch joints for a near-seamless floor.
Enter your floor above and get the exact tile count with waste, the number of boxes to buy, grout in pounds and 25 lb bags, thinset in 50 lb bags by trowel size, and a total material cost estimate. One trip to the store, zero mid-project surprises.
Frequently Asked Questions
How do I calculate how many floor tiles I need?
Divide the floor area in square feet by the area of one tile in square feet, then add 10% for cuts and breakage (15% for diagonal layouts). A 120 sq ft floor with 12x12 tiles needs 120 tiles plus 12 extra, so 132 tiles total.
How much grout do I need for 100 square feet of tile?
For 12x12 tiles with a 1/8 inch joint, plan on about 0.5 to 0.7 bags of grout per 100 sq ft (25 lb bags), so 1 bag covers most rooms under 150 sq ft. Smaller tiles and wider joints need more grout.
How much thinset do I need for floor tile?
A 50 lb bag of thinset covers roughly 40 to 50 sq ft with a 1/4 by 3/8 inch notched trowel, the common choice for 12 inch and larger floor tiles. Smaller tiles with a smaller trowel notch stretch a bag to 60 to 70 sq ft.
What size grout joint should I use for floor tile?
Use 1/16 to 1/8 inch for rectified porcelain with tight, modern grout lines, and 3/16 to 1/4 inch for natural stone or rustic ceramic. Wider joints hide slight tile size variation but need more grout.
Does a diagonal tile pattern use more tiles?
Yes. A diagonal (45-degree) layout wastes 10 to 15% more tile than a straight grid, because every tile along every wall edge needs an angled cut. Herringbone wastes 15 to 20%. Raise your waste allowance when you pick a pattern.
Last updated: 2026 | Grout and thinset figures follow manufacturer coverage charts. This calculator is for estimation only.