Tile Calculator
How many tiles you need comes down to three things in order: the area you are actually covering, the size of one tile with its grout line, and how much you will destroy cutting them to fit. Get those three right and the rest is division. This calculator handles L-shaped rooms and fixtures to subtract, and suggests a waste allowance based on your layout — from 7% for large-format tile on a straight grid to 20% for a diagonal lay.
Break an L-shaped or irregular room into rectangular sections and add them here — their areas are summed automatically.
Waste % auto-fills from the layout pattern — edit it directly to override.
Your tile estimate will appear here
Enter your room and tile dimensions, then click calculate to see how many tiles and boxes you'll need.
Three Steps, in Order
Step 1 — the area you are actually covering. Length times width, then subtract anything you are not tiling: a vanity, a kitchen island, a hearth. For an L-shaped room, split it into two rectangles and add them rather than trying to do it in one go. Measure at floor level, not at the skirting, and measure twice — every number after this one is derived from this one, so an error here scales through the whole job.
Step 2 — the area of one tile, including grout. A 12-inch tile with a 1/8-inch grout line does not occupy 12 inches of floor; it occupies 12.125, because the joint sits between tiles. Squared, that is 147.0 square inches rather than 144 — about 2% more per tile. Small on one tile, a tile or two across a bathroom, and more across a whole floor.
Step 3 — the waste allowance for cutting. This is a percentage added on top, and it is driven by your layout rather than your room. See the table below.
Run those in order for an 8 by 10 ft bathroom in 12-inch tile: 80 sq ft of floor, 1.0 sq ft per tile, so 78.4 tiles to cover it. Add 10% for cutting and you need 87 tiles. In boxes of 10 that is 9 boxes, or 90 tiles.
Area You Skip vs. Tile You Destroy
These are two different things and people net them off against each other, which is the most reliable way to finish a box short.
Area loss is floor you are not covering — the footprint of an island, a vanity, a fitted cupboard. It is subtracted in step 1 and it genuinely saves you tile.
Cut waste is tile that gets ruined making things fit: the perimeter row trimmed to width, the pieces cut around a door frame, the one that snaps wrong. It is added in step 3 and it costs you tile.
A fixture does both at once, and that is the trap. A kitchen island removes its own area and adds a fresh edge that has to be cut around, so it reduces the tile you need by less than its footprint suggests.
Worked through: a 168 sq ft kitchen with a 18 sq ft island leaves 150 sq ft to tile. In 12 by 24 inch large-format tile that is 73.8 tiles to cover, 80 once 7% cut waste is added, which is 10 boxes of 8. Skipping the waste step because “the island saves plenty” would leave you around 6 tiles short of the trimming the island itself creates.
How Much Waste for Your Layout
Starting points, not rules. Push the number up for a small or awkward room, since waste is driven by the length of your cut edges relative to the area — a tiny bathroom full of fixtures wastes proportionally far more than a large open floor.
| Layout | Waste | Why |
|---|---|---|
| Large format (16 in / 40 cm+) | 7% | Fewer tiles overall means fewer cuts, and each offcut is large enough to reuse elsewhere. |
| Straight grid | 10% | The default. Straight cuts along the perimeter, and offcuts often usable on the opposite wall. |
| Herringbone / brick | 15% | The pattern itself forces cuts at every edge, and the offcuts rarely fit anywhere else. |
| Diagonal | 20% | Every perimeter tile is cut on an angle, and the triangular offcut is almost never reusable. The most wasteful common layout. |
The choice is worth real money. That same 8 by 10 ft bathroom takes 87 tiles on a straight grid and 95 on the diagonal — 10 boxes instead of 9, for identical floor area.
Why You Always Round Up Twice
There are two round-ups in this calculation and both go the same way, which is why the tiles you carry home usually outnumber the tiles the job needs.
First, tiles. 86.2 tiles is not a thing you can buy, so it becomes 87.
Then, boxes. Tile is sold by the box and shops do not split them. 87 tiles in boxes of 10 is 9 boxes — 90 tiles, or 11 more than the floor strictly needs.
Treat those spares as part of the job rather than as an overspend. Dye lots vary between production runs, so a box bought next year will not match the floor you laid this year. Keeping a few tiles back is how you repair a cracked tile in five years without relaying the room. Most large retailers also take back unopened, undamaged boxes within about 90 days, so an extra box is usually a cheap hedge against a delay.
Irregular Rooms and What Tile Actually Costs
L-shaped rooms and fixtures you won't tile under
Most rooms aren't clean rectangles. A bathroom might have a jog around a closet, or a kitchen might have a peninsula. Break the space into rectangles you can each measure (an L-shaped room is almost always two) and add each one as a separate section above; the calculator sums the areas for you. Then subtract anything with a footprint you won't tile under, like a kitchen island or a built-in vanity cabinet, in the subtract-fixtures field. Skipping this step means paying for tile you'll never lay, sometimes 5-10 sq ft of wasted material on an average kitchen island alone.
Example 3: Kitchen floor with an island, plus total cost
A 12 ft × 10 ft kitchen (120 sq ft) has a 3 ft × 3 ft island (9 sq ft) you won't tile under, leaving 111 sq ft to cover. With 12x12 inch tile, a 1/8 inch grout line, a straight grid layout, and 10% waste, that's 120 tiles, or 12 boxes at 10 tiles per box. At $45 a box, the tile itself runs about $540, before thinset, grout, and spacers.
Waste isn't one number: it moves with pattern and tile size
The flat "add 10%" advice you'll see everywhere is a starting point for a straight grid, not a rule. Diagonal layouts run closer to 20% waste because every edge tile needs an angled cut. Herringbone and brick patterns sit around 15%. Large-format tile (16 in / 40 cm and up) often needs less than 10%, sometimes as low as 5-7%, simply because fewer, bigger tiles mean fewer cut edges in the same room. Small mosaic and subway tile trend the other way. Picking a layout pattern in the calculator sets a sensible default waste % automatically, and you can still override it by hand.
Quick Answer
Divide the area you are covering by the area of one tile including its grout line, then add a waste percentage for cutting: 10% for a straight grid, 20% for diagonal, 15% for herringbone, 7% for large-format tile. Round the tile count up, then divide by tiles per box and round up again. An 8 by 10 ft bathroom in 12-inch tile needs 78 tiles to cover the floor, 87 once 10% waste is added, which is 9 boxes of 10.
How It Works: Formula & Variables
Tiles Needed = ((Room Area − Fixture Area) ÷ Tile Area) × (1 + Waste % ÷ 100)
- Room Area
- Length × width of the room (summed across sections for L-shaped rooms), or entered directly if you already know the square footage.
- Fixture Area
- The footprint of anything you won't tile under, like an island or vanity. Optional, subtracted before the tile count.
- Tile Area
- Tile width × tile length, with the grout line width added to each side.
- Waste %
- Extra tiles bought to cover cuts, breakage, and future repairs, set by your layout pattern or entered directly.
- Boxes Needed
- Tiles needed ÷ tiles per box, rounded up to the next whole box.
Worked Examples
Example 1: Bathroom floor, feet and inches
An 8 ft by 10 ft bathroom floor is 80 sq ft, laid in 12 by 12 inch tile with a 1/8 inch grout line. With grout, each tile covers 1.0 sq ft, so the floor takes 78.4 tiles — not 80, because the grout line makes each tile slightly larger than a square foot. Adding 10% for a straight grid gives 86.2, so you buy 87 tiles. In boxes of 10 that is 9 boxes (90 tiles, 11 spare).
Example 2: Kitchen floor, metric
A 4 m by 3 m kitchen is 12 m², laid in 30 by 30 cm tile with a 3 mm grout line. Each tile covers 0.0918 m² with the joint, so the floor takes 130.7 tiles. At 10% waste that is 144 tiles, or 15 boxes of 10. Ignoring the grout line here would suggest 0.09 m² a tile and 133 tiles, which understates the count.
Example 3: Kitchen with an island, large-format tile
A 12 by 14 ft kitchen is 168 sq ft, less a 3 by 6 ft island footprint at 18 sq ft, leaving 150 sq ft to tile. In 12 by 24 inch large-format tile that is 73.8 tiles, and because large format on a straight grid wastes only about 7%, you need 80 tiles — 10 boxes of 8. The island reduced the area, but it also added a cut edge, which is exactly why the waste percentage still applies to the reduced figure.
Example 4: The same bathroom, laid diagonally
Identical 80 sq ft floor and identical tile, but turned 45 degrees. The floor still needs 78.4 tiles to cover, but every perimeter tile is now cut on an angle and the offcut is a triangle that fits nowhere, so waste rises to 20%. You need 95 tiles, or 10 boxes — 1 more than the straight grid, for the same room.
Key Concepts
Waste allowance: Cutting tiles to fit around edges, corners, and fixtures always produces some unusable offcuts. Buying extra avoids a second trip to the store if a tile breaks later.
Grout line width: The grout line adds a small amount to each tile's effective footprint, which can slightly increase the total tile count for large areas.
Box coverage: Tiles are usually sold by the box, not individually. Always round up to the next full box, since stores rarely sell partial boxes.
Pattern and size drive waste more than any flat rule: a straight grid in large-format tile might need only 5-7%, while a diagonal layout in small mosaic tile can need 20% or more. Pick a pattern in the calculator and it'll suggest a starting point.
Store return policies: Most big-box retailers accept unopened, undamaged boxes back within 90 days. That's a real safety net: when in doubt, rounding up to a full extra box is usually cheaper than a delay waiting on a reorder.
Common Mistakes
Skipping the waste allowance: Ordering the exact number of tiles needed often leaves you short once cuts and breakage are accounted for.
Mixing units: Entering room dimensions in feet but tile sizes in centimeters (or vice versa) will throw off your tile count. Use the unit toggle to keep everything consistent.
Ignoring grout lines: For large rooms with many tiles, ignoring the grout line width can lead to a noticeable undercount.
Rounding down on boxes: Always round up to the next full box. Buying one box short can mean a delayed project waiting on a reorder, sometimes from a different dye lot.
Tiling for space you'll never see: Counting the floor under a kitchen island or a built-in vanity as tiled area wastes money on tile that gets thrown away or stored indefinitely.
Treating mosaic sheets as single tiles: Mosaic and subway mesh sheets are sold and counted by the sheet, not the tile. Using the sheet's dimensions as your "tile size" in the calculator gets this right; using one tiny tile's dimensions will wildly overcount.
Frequently Asked Questions
Divide the area of your room by the area of one tile (including the grout line), then add 10% extra for cuts, waste, and breakage. For example, a 100 sq ft room with 12x12 inch tiles needs about 100 tiles, plus 10 extra, so 110 tiles.
Tile overage is the extra tile you buy beyond the exact square footage of your room, to cover cuts, breakage, and mismatched dye lots on future repairs. The right number depends on your layout, not a single rule: about 10% for a straight grid, 15% for herringbone or brick patterns, and 20% for diagonal layouts, since each cut edge produces an offcut you can't reuse. Large-format tile (16 in / 40 cm or bigger) usually needs less, closer to 7%, because fewer, bigger tiles mean fewer cuts per square foot.
First calculate the total number of tiles needed (including waste), then divide by the number of tiles per box and round up. If you need 110 tiles and each box contains 10 tiles, you need 11 boxes.
Yes, slightly. A wider grout line increases the effective footprint of each tile, which can reduce the number of tiles that fit in a given area. For most home projects this effect is small, but it matters more for large rooms or thick grout lines.
Use the unit toggle on this calculator to switch between feet/inches and meters/centimeters. The calculator handles the conversion automatically so your tile count stays accurate either way.
It depends entirely on your tile size. For a common 30x30 cm tile, each one covers 0.09 m², so you need about 11.1 tiles per square metre before overage. For a larger 60x60 cm tile, each covers 0.36 m², so you need about 2.8 tiles per square metre. Switch this calculator to metric units and enter your tile size in centimetres to get an exact count for your project.
Split the room into rectangles you can measure separately. An L-shaped bathroom is usually two rectangles, for example. Use the calculator's "Add section" button to enter each one; it sums the areas for you. Then subtract any fixed footprint you won't tile under, like a kitchen island or a built-in vanity, in the subtract-fixtures field. Tiling under a fixture wastes tile and money for no benefit, so leave it out of the count entirely instead of adding it as extra waste.
Yes. Waste comes from cut pieces you can't use, and cuts happen at edges, so the more tile edges in a room, the more waste. A 24x24 inch tile covers 16 times the area of a 6x6 inch tile, so a room needs far fewer of them, which means far fewer cut edges. That's why large-format tile is usually estimated at 5-8% waste while small mosaic or subway tile is closer to 15%, even in the exact same room.
Most large retailers (Home Depot, Lowe's, Floor & Decor) accept unopened, undamaged boxes for return or store credit within 90 days, though policies vary by location and sometimes by product line. That's why it can make sense to round up rather than down when you're unsure. Buying one extra box you can return is a much smaller hassle than being one box short mid-project and having to match a new dye lot.
No, and this trips people up. Mosaic tile is usually sold and priced by the sheet (often 12x12 inches), with dozens of small tiles mesh-mounted to each sheet, so you're buying sheets, not individual tiles. If your tile is mosaic, calculate the area of one sheet (not one tile) and divide your room area by that instead. Check the product listing for the sheet dimensions.
Enter a price per box in the calculator alongside tiles per box, and it multiplies that by the number of boxes needed (already rounded up) to give a total. This covers tile only, so budget separately for thinset, grout, spacers, and a trowel, which typically add another 10-20% on top of the tile price for a DIY job.
Related Calculators
Not sure of the area yet?
Everything here depends on step 1, so get that right first. The area calculator handles rectangles, triangles and circles if the room is an awkward shape, and the square footage and flooring calculator works out total square footage across several rooms and covers materials sold by the square foot rather than by the tile — laminate, vinyl and carpet. Come back here once you have a number.
Assumptions
- The grout line is added to both dimensions of the tile, because the joint sits between tiles. This raises the tile count slightly against a calculation that ignores it.
- Waste percentages are industry starting points, not guarantees. A small room with many fixtures wastes proportionally more than a large open floor at the same layout.
- Tiles and boxes are both rounded up, never down. Partial boxes are not generally sold.
- No allowance is made for tiles damaged in transit, or for a deliberate attic stock beyond the spares the box round-up leaves you.