Tile exactly right.
Tiles and boxes needed for any floor or wall. Accounts for cuts, waste, and patterns so you only make one trip to the store.
How we calculated this
The calculator computes the floor area (length × width), divides by the area of a single tile (converted to the same unit), and multiplies the result by 1 plus the waste factor. Tile dimensions are listed in inches (imperial) or centimeters (metric) and internally converted to square feet or square meters.
Waste factor covers cuts along edges, miscellaneous breakage during installation, and keeping a few spare tiles for future repairs. The right factor depends on your layout: 10% is fine for straight-lay patterns, 15% for 45-degree diagonals, 20% for herringbone or other patterns with lots of cuts.
Tile count is rounded up to the nearest whole tile because you can't buy fractional tiles. Boxes are rounded up to the next whole box — you buy by the box, not the tile.
Variation between tiles from different production runs is real. Always buy all your tile at once from the same lot number, and keep 1-2 full boxes of extras for repairs years later (specific patterns and colors get discontinued).
The dye lot problem nobody warns you about
A tile installer in Phoenix told me about the call he dreads most. It comes at 2 PM on a Saturday: "I am three tiles short and the store is out of my dye lot." This happens twice a month during renovation season. The homeowner measured the floor, bought exactly that many tiles, and forgot that every row along the wall needs a cut. Every cut creates a scrap piece. Some scraps start the next row, some go in the trash because they are an inch wide and fragile.
Three tiles short on a porcelain floor means pulling out a tile from behind the toilet to use in a visible spot, or waiting two weeks for the same dye lot to ship from the warehouse. And dye lot is not a technicality. Tile is manufactured in batches. Color varies slightly between batches, sometimes enough to see on the wall under natural light. Order all your tile from the same dye lot, and order 10 percent more than you calculate. That extra box is your insurance against a color mismatch that cannot be fixed without tearing everything up.
How we calculated these numbers▾
Waste percentages follow Tile Council of North America (TCNA) installation guidelines. Grout coverage rates calculated from joint geometry (width × depth × tile perimeter / tile area). Tile pricing reflects 2026 retail from Floor & Decor, Home Depot, and MSI distributor pricing. Substrate recommendations follow ANSI A108 standards.
First question: can your subfloor handle tile?
Before calculating how many tiles to buy, make sure the surface underneath can support them. This is the step most DIYers skip, and it is the reason most DIY tile floors fail within two years. Tile and grout are rigid. Subfloors flex. When rigid material sits on a flexing surface, grout cracks, tiles pop, and water gets underneath.
Three checks before ordering materials. First, level: place a 6-foot straightedge on the subfloor and look for gaps. Anything over 3/16 inch needs leveling compound ($0.50 to $1.00 per square foot). Second, moisture: on concrete subfloors, test with a calcium chloride kit. Readings over 3 pounds per 1,000 square feet per 24 hours mean you need a moisture barrier. Third, bounce: walk across the room. If the floor visibly flexes underfoot, the joists may need sistering or blocking before tile goes down. Flexible subfloors crack rigid tile installations within a year.
The most common DIY tile failure is tiling directly on a plywood subfloor without backer board. A quarter-inch cement backer board (Durock, HardieBacker) costs $0.50 to $1.00 per square foot and solves this permanently. It adds 30 minutes of work and prevents 100 percent of flex-related failures.
How waste changes with size and pattern
Diagonal layouts add 15 percent waste regardless of tile size because every edge cut is at an angle, producing triangular offcuts that cannot start the next row. Herringbone is even worse: 18 to 20 percent. If you have your heart set on a diagonal or herringbone pattern, budget accordingly. The tile is the same price per square foot either way, but you need 10 to 15 percent more of it.
Composite illustration based on typical project dimensions, regional contractor pricing, and 2026 material costs. Not a specific real project.
What tile actually costs
DIY | Professional | |
|---|---|---|
| Tile (100 ft² porcelain) | $500 | $500 |
| Thinset mortar | $25–50 | Included |
| Grout | $20–40 | Included |
| Backer board (if needed) | $100–150 | Included |
| Wet saw rental | $50–75/day | Included |
| Labor | $0 (2–3 days) | $500–1,500 |
| Total for 100 ft² | $695–815 | $1,000–2,000 |
Tile is DIY-able for floors with basic straight cuts. Shower walls, mosaics, and large-format tile on walls should be hired out. The margin for error is thin and the rework cost is high.
The wet saw rental is the line item people forget. A quality tile wet saw costs $50 to $75 per day to rent. You cannot cut porcelain with a score-and-snap cutter (it shatters), and you cannot cut curves or notches around toilet flanges without a wet saw. Budget for at least a full day rental, possibly two. Returning the saw with the tank full of milky water earns you a cleaning surcharge at most rental shops, so drain and rinse it before bringing it back.
Grout: the part that ties it together
A 25-pound bag of unsanded grout covers roughly 35 to 95 square feet depending on tile size and joint width. A 100 square foot floor with 12×12 tile and 1/8-inch joints needs about 2 bags. The same floor with 1/4-inch joints needs 5 bags. That is a real cost and time difference. Wider joints also take longer to apply and are harder to keep even. Use the grout calculator for exact quantities based on your tile and joint dimensions.
Sanded grout is for joints wider than 1/8 inch. Unsanded grout is for 1/8 inch and narrower. Using unsanded grout in wide joints causes cracking because it shrinks too much. Using sanded grout in narrow joints is difficult to work because the sand grains do not fit. Match the grout type to your joint width.
Layout planning saves the entire project
Before opening the mortar, dry-lay your first two rows of tile without adhesive. Start from the center of the room, not from a wall. This shows you where the cuts fall at the edges and lets you adjust the starting point so that both sides of the room have cuts wider than half a tile. A bathroom floor with a full tile along the tub and a 1-inch sliver along the opposite wall looks like a mistake. Centering the layout prevents this.
For shower walls specifically, the shower tile calculator handles three-wall layouts with niche openings. For kitchen backsplashes, use the backsplash calculator, which subtracts outlets and window openings from the tiled area.
One last thing. Lippage. When tiles are not pressed to equal depth in the mortar bed, one edge sits higher than its neighbor. On large format tiles (12×24 and bigger), even 1/32 of an inch of lippage catches socks and looks terrible in raking light. Use a leveling clip system (Raimondi, Spin Doctor, or similar) for any tile larger than 12×12. The clips cost $0.10 to $0.25 each and add $30 to $60 to a typical bathroom floor. They guarantee flat tile edges with zero guesswork. Professional tilers use them routinely. DIYers who skip them regret it the first time they walk across the floor barefoot.
Sources
- Tile Council of North America — Installation Handbook — Industry standards for waste factor by pattern
- Home Depot — Tile Buying Guide — Reference for buying tile in lots and boxes
Frequently asked
How much extra tile should I buy?
10% is the minimum for simple straight-lay patterns on rectangular floors. Add 5% for each additional complexity: diagonal layouts (15%), herringbone or chevron (20%+), irregular room shapes, many obstructions. When in doubt, buy more — discontinued lots are hard to match later.
Why do I need to buy all tile at once?
Tile is manufactured in batches called 'lots' or 'dye lots'. Slight color and size variations exist between lots — invisible individually, but visible when tiles from different lots are installed next to each other. Always buy enough for the entire project plus spares from the same lot.
How many tiles are in a typical box?
Varies by tile size: 12×12 tiles usually 10-15 per box; 12×24 typically 6-8; 18×18 about 6; 24×24 about 3-4. Always check the specific tile you're buying — the calculator uses your input for tiles per box.
Does this include the grout?
No, this calculates tile quantity only. Grout is a separate purchase. As a rough guide, you need about 1-2 pounds of grout per 10 sq ft for 1/8-inch joints. Use the grout calculator for a precise number.
How much waste should I expect with 24×24 tiles?
Larger tiles produce more waste because each edge cut leaves a larger unusable piece. For 24×24 tiles on a straight-lay pattern, 12-15% waste is realistic — more if the room has complex edges or obstructions.
Do I calculate wall tile the same way?
Yes — the math is identical. Enter the wall dimensions as length and width. For showers, calculate each wall separately and add them. Subtract large openings (windows, niches) only if they're bigger than a few square feet.
What about diagonal or herringbone layouts?
Bump the waste factor up: 15% for diagonal straight lay, 20% for herringbone or chevron, 25% for complex patterns with many cuts. These layouts require cutting tiles at angles, which produces more unusable scrap per cut.
Can I use this for subway tile or large-format tile?
Yes — use the closest matching preset, or enter the tile size if you need something non-standard. For subway tile (3×6), the math is the same but you'll need many more tiles because each one covers less area.
Was this calculator helpful?