How to use the tile calculator
- Choose Length x width (enter your room's dimensions) or Enter sq ft directly if you already know the area.
- Enter your tile length and width, in inches.
- Pick a grout joint width -- 1/8 in is the standard default; see below for when to use a different one.
- Pick a layout pattern to set the waste allowance, and enter how many tiles come in one box.
- Read the tiles needed, tiles to buy (with waste) and boxes to buy below.
No signup, no email and no address lookup -- everything runs in your browser.
How many tiles do I need? The formula
Effective tile area = (tile length + grout joint) × (tile width + grout joint), converted from inches to sq ft.Tiles needed = room area ÷ effective tile area, rounded up.
Worked example: a 120 sq ft room (10 × 12 ft) tiled with 12 × 12 in tile and a standard 1/8 in grout joint. Effective tile footprint: 12.12 × 12.12 in = 1.021 sq ft per tile. Tiles needed: 120 ÷ 1.021 = 118 tiles before waste. With a 10% straight-lay waste allowance, that's 130 tiles to buy, or 13 boxes at 10 tiles per box.
How do I account for grout lines?
Every tile sits next to a grout joint, so the floor area one tile "claims" -- tile plus its share of the surrounding joint -- is slightly bigger than the bare tile itself. A wider joint means each tile's effective footprint is a little larger, which can nudge the tile count up on a big job. For a 12 × 12 in tile over the 120 sq ft example above:
| Grout joint | Effective tile area | Tiles needed |
|---|---|---|
| 1/16 in | 1.01 sq ft | 119 |
| 1/8 in (default) | 1.021 sq ft | 118 |
| 1/4 in | 1.042 sq ft | 116 |
1/8 in is the standard default for most modern floor and wall tile; use 1/16 in for rectified tile with precisely square edges, and 3/16-1/4 in for non-rectified, rustic or large-format tile on an uneven floor.
How much extra should I buy for waste?
- Straight (grid) lay: 10% -- the lowest-waste layout, since cuts are simple and offcuts are reusable along the opposite wall.
- Diagonal, herringbone or staggered: 15% -- more angled cuts at the perimeter, and offcuts are less likely to be reusable.
- Complex pattern: 20% -- a wider margin for intricate custom layouts, multiple tile sizes or heavy pattern-matching (this option is this calculator's own extra-margin extension, not tied to a single published source the way the first two are).
On the 120 sq ft example, that's the difference between 130 tiles at 10% waste and 142 tiles at 20%.
How many boxes of tile do I need?
Boxes to buy = tiles to buy (after waste) ÷ tiles per box, rounded up. Box coverage is product-specific -- it varies by tile size, thickness and manufacturer -- so this calculator asks you to enter it rather than assuming a number; check the box itself or the product page for the exact count. For the 120 sq ft example (130 tiles to buy), that's 13 boxes at 10 tiles per box, or 22 boxes at 6 tiles per box.
Large-format tile example
The same formula works for any tile size, including large-format plank tile. A 12 × 24 in plank with a 1/8 in joint has an effective footprint of about 2.03 sq ft. A 150 sq ft room needs 74 tiles before waste, 82 tiles after a 10% straight-lay allowance, or 11 boxes at 8 tiles per box.
Measuring an irregular room first
This calculator's "Length x width" mode covers one rectangle. For an L-shaped room, a room with a cut-out, or a room measured in feet and inches, work out the total square footage first with the square footage calculator, then switch this calculator to "Enter sq ft directly" and type that total in.
Frequently asked questions
How many tiles do I need for a room?
Divide your room's area (in sq ft) by one tile's effective footprint (its length x width, each plus the grout joint, converted to sq ft), then round up. A 120 sq ft room (10 x 12 ft) tiled with 12 x 12 in tile and a standard 1/8 in grout joint needs 118 tiles before any waste allowance. The calculator above does this automatically for any room and tile size.
How do I calculate tile for a floor? The formula
Effective tile area (sq ft) = (tile length + grout joint) x (tile width + grout joint), both converted from inches to feet. Tiles needed = room sq ft ÷ effective tile area, rounded up. For a 12 x 12 in tile with a 1/8 in joint, the effective footprint is 12.12 x 12.12 in, or 1.021 sq ft per tile.
How do I account for grout lines when calculating tile?
A grout joint adds a sliver of floor area to every tile's effective footprint, so a wider joint means slightly fewer, slightly "bigger" effective tiles fit -- but each one covers marginally more area, which barely changes the total for a small room and adds up on a large one. For the same 12 x 12 in tile, a narrow 1/16 in joint needs 119 tiles for our 120 sq ft example, while a wide 1/4 in joint needs 116. The calculator above lets you pick 1/16, 1/8, 3/16 or 1/4 in.
How much extra should I buy for waste?
Add 10% for a straight (grid) lay, 15% for a 45-degree diagonal, herringbone or staggered pattern, and up to 20% for a complex custom pattern with a lot of cuts. On the 120 sq ft example, that's 130 tiles to buy at 10% waste versus 136 at 15% and 142 at 20%.
How many boxes of tile do I need?
Divide tiles to buy (after waste) by however many tiles come in one box, then round up -- box coverage is product-specific, so check the box or the product page rather than assuming a number. The 120 sq ft example needs 130 tiles, which is 13 boxes at 10 tiles per box, or 22 boxes at 6 tiles per box.
What grout joint width should I use?
1/8 in is the standard default for most modern floor and wall tile. Use a narrower 1/16 in joint only for rectified tile (precisely cut, square edges); use a wider 3/16-1/4 in joint for non-rectified tile, subway tile with built-in spacer lugs, or large-format tile on a floor that isn't perfectly flat. Check your tile manufacturer's own installation instructions when in doubt.
How do I calculate tiles for a diagonal or herringbone layout?
The tile count formula is the same -- room area ÷ effective tile area -- but diagonal and pattern layouts create far more angled cuts at the walls, so they need a bigger waste allowance (this calculator uses 15%, versus 10% for a straight grid lay). Diagonal and herringbone jobs also cut more slowly and use more blade, so budget extra time as well as extra tile.
How do I calculate tile for a large-format plank tile, like 12 x 24 in?
The same formula applies: a 12 x 24 in plank tile with a 1/8 in joint has an effective footprint of about 2.03 sq ft. A 150 sq ft room needs 74 tiles before waste, 82 after a 10% straight-lay allowance, or 11 boxes at 8 tiles per box.
Can I enter my room area directly instead of length and width?
Yes -- switch the "Room area" toggle above to "Enter sq ft directly" and type the number in. This is handy if you've already measured an irregular room (add up its sections with the square footage calculator first) or if a contractor gave you a total area instead of dimensions.
Do I need to give my address or sign up to use this calculator, and is my data saved anywhere?
No. Enter your room and tile dimensions directly -- there is no signup, no email and no address lookup. Your entries are saved only in your own browser (so they are there next time you open this page on the same device); nothing is sent to our servers.