Tile Calculator: Square Footage, Tiles and Boxes
Enter your dimensions and you get both numbers: the square footage to cover, and the box count to actually buy. Grout joints, layout pattern and waste are all in the math.
Your room and your tile
Your square footage and what to buy
- Square footage to cover — sq ftYour area, after deducting anything you entered.
- Tiles to buy — tilesBare coverage plus the waste allowance for your layout.
- Boxes to buy — boxesRounded up. Buy them in one trip so they share a dye lot.
- Tiles for the bare area — tilesNo waste at all. Never order this number.
- Waste allowance applied — %
- Square feet to order — sq ftUse this figure if your tile is priced by the square foot.
- Weight of the order — lbWhat actually arrives, counting whole boxes. Worth knowing before you promise to fetch it yourself.
- Weight of one box — lbThe number that decides whether this is a car trip or a delivery.
How to use this calculator
- Measure the room, not the tile. Length and width in whatever form you wrote them down — 12, 12', or 12' 6" all work. Deduct the footprint of anything permanent that will not be tiled under.
- Pick your tile size. The preset fills in the dimensions, thickness and box coverage. If you already have the box in front of you, choose Custom and copy the three numbers off it — they beat any preset.
- Set the grout joint before the pattern. Joint width changes how much surface each tile really covers, and on small tile it changes the count more than the waste allowance does.
- Choose the layout you are actually laying. This sets the waste allowance on its own: a diagonal or herringbone run generates offcuts you cannot use anywhere else.
- Read the box count, not the tile count. Tiles are what you install; boxes are what you buy and pay for. The square footage line is there for tile priced by the foot.
- Check the weight before you plan the trip. Weight per box is what decides whether this goes in a car or on a delivery. Nine boxes of large-format porcelain is most of a half-ton.
How to measure your square footage
Measure the floor, not the room. Those are different numbers the moment there is a vanity, a kitchen island or a tub in the way.
Break the space into rectangles, measure each one, and add them up. An L-shaped kitchen is two rectangles. A bathroom with a linen closet is one rectangle minus a small one. Measure at the floor line rather than at counter height, because baseboards, drywall bows and out-of-square walls all live down there and none of them are where you think they are.
Two habits worth keeping:
- Measure both ends of every run. Rooms are rarely square. If one end of a 10 foot wall is 10' 0" and the other is 10' 1½", use the larger figure. Tile does not stretch.
- Only deduct what is genuinely permanent. A tub, a shower base, a run of cabinets that is staying: deduct those. A freestanding fridge or a washing machine: do not. You want tile under anything that might move or be replaced later.
For walls, "length" and "width" become width and height. A backsplash is the run length by the height from countertop to the underside of the upper cabinets.
The math behind the tile count
The calculation everyone gets wrong is the first one, and it is the reason two calculators give two different answers for the same room.
A tile does not cover its own face area. It covers its face plus one grout joint on two sides, because every tile in the field shares a joint with its neighbors. That rectangle is the module:
module area (sq ft) = (tile width + joint) × (tile length + joint) ÷ 144
tiles for bare area = net area ÷ module area
tiles to buy = tiles for bare area × waste factor, rounded up
For a 12 × 24 inch tile with a 1/8 inch joint, the module is 12.125 × 24.125 inches — about 2.03 square feet instead of the 2.00 you get from the face alone. That is a 1.3% difference. On a small bathroom it disappears into the rounding. On 800 square feet of large-format porcelain it is around ten tiles, which is a full box you did not need to carry home.
The last row and the last column of a field have no joint on their outer edge, so this method is very slightly conservative. It is a fraction of one tile, and the waste allowance swallows it many times over.
How much waste to allow
Waste tracks cut edges, not floor area. A big open rectangle wastes almost nothing. A narrow bathroom with a doorway, a toilet flange and a vanity wastes a lot, because nearly every tile against a wall gets cut and most offcuts are the wrong shape to use anywhere else.
The allowances built into the calculator are the ones tile setters normally quote:
| Layout | Typical allowance | Why |
|---|---|---|
| Straight / stacked grid | 10% | Square cuts only; many offcuts start the next row |
| Offset / running bond | 12% | Half the offcuts are the wrong length to reuse |
| Diagonal (45°) | 15% | Every perimeter tile is a triangle |
| Herringbone or chevron | 20% | Angled cuts at both ends, almost nothing is reusable |
Add another 5% on top if any of these are true: the room has more than four corners, you are tiling around a bay or a fireplace, the tile is a natural stone with visible variation you will want to sort through, or the pattern has a direction you have to keep consistent.
Take the allowance down rather than up in only one case: a large, genuinely rectangular open floor with a straight grid layout and no obstacles. Even then, 8% is as low as it is worth going.
Buy boxes, not tiles
Nobody sells you 214 tiles. They sell you boxes, and the box is the unit that decides what you actually spend.
Coverage per box is printed on the carton, and it moves far more than people expect. Not by a little: we went through the current 12 × 24 porcelain listings at a large US retailer and found cases running from 11.64 to 16 square feet. Same nominal tile, a 37% spread, and it lands straight on your box count — 134 square feet of 12 × 24 is nine boxes at 15.5 and twelve boxes at 11.64.
The spread is not uniform across formats. 3 × 6 subway is remarkably consistent, with 12.5 square feet per case dominating the listings, and 6 × 24 wood-look plank clusters tightly around 14.55. It is the squares that scatter: 12 × 12 and 24 × 24 turned up everything from 10 to 19 square feet a case.
That is why the size presets above fill in a typical box coverage rather than a definitive one, and why the field stays editable. The preset gets you a sensible answer in one click. Your own carton gets you the right one.
Two rules that cost nothing and save a lot:
- Buy the whole job in one trip. Tile is made in dye lots. A box bought three months later can be visibly different in color or shade under the same light, and there is no fixing that once it is set.
- Keep a spare box. Not a spare tile — a box. When a tile cracks in year four because someone dropped a cast-iron pan on it, the replacement has to come from your garage, because the product will have been discontinued or the lot will have moved on.
Where this number still goes wrong
The calculator is honest about area and honest about waste. It cannot see four things, and all four have cost people a return trip:
- Where the layout starts. A field centered on the room wastes more than one started from the most visible wall, because you end up with two narrow cut edges instead of one. Dry-lay a row before you commit.
- Tile you break. Everybody breaks a few. Scoring a large-format tile 2 inches from the edge is a coin flip even with a good cutter.
- Damage in transit. Open every box on delivery. A cracked tile at the bottom of a carton is the supplier's problem for about a week, then it becomes yours.
- The pattern's own repeat. Herringbone and chevron consume tile in pairs and have a fixed repeat; awkward room dimensions can push you into an extra box no formula predicts.
Worked example
A bathroom floor, 12 feet by 10 feet, with a 5 foot by 2.5 foot tub to deduct. Tile is 12 × 24 porcelain, 1/8 inch joints, laid in a running bond, sold at 15.5 square feet per box.
- Gross area: 12 × 10 = 120 sq ft
- Deduct the tub: 5 × 2.5 = 12.5, so net area = 107.5 sq ft
- Module: (12 + 0.125) × (24 + 0.125) ÷ 144 = 2.031 sq ft per tile
- Bare coverage: 107.5 ÷ 2.031 = 53 tiles
- Running bond allowance, 12%: 53 × 1.12 = 59.3 → 60 tiles
- Square feet to order: 60 × 2.00 = 120 sq ft
- Boxes: 120 ÷ 15.5 = 7.7 → 8 boxes
Eight boxes covers 124 square feet against a net area of 107.5. That sounds generous until you have cut sixteen tiles around a toilet flange and a doorway, and it leaves you the better part of a spare box for the repair you will need in a decade.
What this calculator assumes
- Coverage is worked out per tile module — the tile plus one grout joint on two sides. On the final row and column there is no joint, which makes the result marginally conservative. The waste allowance absorbs it many times over.
- The waste percentages come from the layout you pick and are typical trade allowances, not a manufacturer specification. A room full of jogs, niches and diagonal walls needs more.
- Box counts assume every box in the run holds the coverage you entered. Check the box: coverage varies between production runs of the same product.
- Nothing here accounts for tile that arrives broken, or for the two or three you will break yourself. That is what the waste allowance is for.
- The preset sizes fill in a typical tile so you are not starting from a blank form. The dimensions are the nominal format and are reliable; the thickness is typical for that format rather than a specification, and the box coverage is a middle-of-the-road figure, not a standard.
- Box coverage is the one number you should check against your own box. Surveying current 12 x 24 porcelain listings at a large US retailer turned up cases from 11.64 to 16 square feet — a 37% spread for the same nominal tile. 3 x 6 subway is far more consistent, with 12.5 square feet dominating, and 6 x 24 plank clusters tightly around 14.55. Squares vary the most.
- Weight is worked out as thickness x density x area, using nominal densities of 150 lb per cubic foot for porcelain, 125 for ceramic and 165 for natural stone. It counts the tile only: no mortar, no backer board, no pallet. The order weight is based on whole boxes, because whole boxes are what turn up.
Common questions
How much extra tile should I actually buy?
For a straight grid in a simple rectangular room, 10% is the normal trade allowance. Running bond needs a little more, a 45° diagonal more again, and herringbone the most, because every offcut is a wedge you cannot use anywhere else. If the room is broken up by closets, a bay or a fireplace, add another 5% on top — waste tracks the number of cut edges, not the floor area.
Do I include the grout joint in the calculation?
Yes, and most calculators do not. A 12×24 tile with a 1/8 inch joint covers 12.125×24.125 inches, which is about 1% more than the tile face. On a small bathroom that is nothing. On 800 square feet of large-format tile it is roughly eight tiles — more than a full box.
Should I buy an extra box on purpose?
For anything you cannot easily replace, yes. Tile is made in dye lots and a batch bought a year later will not match. One spare box in the garage is cheap insurance against a cracked tile in the middle of the floor.
Why does the box count sometimes jump by two?
Because boxes are indivisible and the calculation rounds up twice — once on tiles, once on boxes. If you are one or two tiles into a new box, it is worth revisiting the layout or the joint width before you buy it.
How much will my tile weigh?
The calculator gives you two figures: the weight of one box, and the weight of the whole order counting whole boxes. The box number is the one that matters on the day. A box of 12 x 24 porcelain runs around 73 pounds, so ten boxes is roughly three quarters of a ton — well past what most cars will take, and past what most people should be lifting one at a time. Subway tile is much lighter per box, around 39 pounds. If the order weight surprises you, price the delivery before you book the van.
Where these numbers come from
- Waste allowances are the ranges commonly specified by tile setters and echoed in the TCNA Handbook's guidance on layout and cut waste. They are planning figures, not a warranty.
- Coverage per box is always printed on the carton and varies by production run — the field defaults to 15.5 sq ft only because it is a common figure for 12×24 porcelain.
- Preset box coverages were taken from the spread of real product listings rather than from any single manufacturer, and are declared as typical rather than standard. Your own box is the authority.
- Tile densities for the weight figure are the usual nominal values for each material: roughly 150 lb/cu ft for porcelain, 125 for ceramic and 165 for natural stone.
Last checked 2026-08-20.