Tile Calculator
Tiling a bathroom, kitchen backsplash, or floor? Enter your total area and tile dimensions to calculate exact tile count, box count with waste, and estimated grout needed.
Results
Waste is set by the pattern, not by the room
Tile is ordered by area plus a waste allowance, and the allowance is the part people get wrong. It is not a hedge against mistakes — it is the arithmetic consequence of the layout, because every tile cut at a wall or a corner leaves an offcut too small to use anywhere else.
Formula: tiles = area × waste factor ÷ tile size in sq ft, rounded up
| Layout | Allowance | Why |
|---|---|---|
| Simple rectangle, straight grid | 5% | Cuts on two walls only |
| Standard room, straight grid | 10% | The working default |
| Diagonal, herringbone, chevron | 15% | Every perimeter tile is cut at an angle |
| Curves, alcoves, many corners | 15 to 20% | Offcuts are unusable |
Large-format tile pushes the number up rather than down. A 4 in strip cut from a 24 × 24 in tile wastes most of that tile, where the same strip off a 12 × 12 wastes a quarter as much material.
Boxes, not tiles, are what you buy
Tile is sold by the box and boxes are not broken. This calculator assumes 15 sq ft per box, which is a common size, but it varies by manufacturer and by format — mosaic sheets and large-format tile often come 8 to 12 sq ft to a box. Check the actual figure on the box before ordering, because rounding up to a whole box can add several square feet on its own.
Order the entire job in one purchase and check that every box carries the same lot or batch number. Tile is fired in batches and color varies measurably between them. A box opened halfway through the floor from a different lot is visible under raking light, and the fix is to pull up finished work.
What sits under and between the tile
The estimate here covers tile and grout. A tiled floor also needs thinset mortar, which runs roughly one 50 lb bag per 40 to 50 sq ft depending on trowel size, and the trowel size is set by the tile: larger tile needs a deeper notch and consumes more mortar per square foot.
Grout is estimated at 0.5 lb per square foot, which is a reasonable average for 12 × 12 tile at a 1/8 in joint. The real figure swings hard with tile size and joint width — small mosaic at a wide joint can take five times as much as large-format at a tight one. Backer board or an uncoupling membrane is a separate line item again, and it is not optional over plywood or in a wet area.
Keep the leftovers
The offcuts are waste, but the whole spare tiles are not. Keep a full box, or at least half a dozen tiles, somewhere dry. Cracked tiles get replaced one at a time years later, and by then the line is discontinued or the lot number is long gone. A single replacement tile in a slightly different shade sits in the middle of a floor for the rest of its life.
Frequently asked questions
How much extra tile should I buy for waste?
Ten percent for a standard room in a straight grid, 5% for a simple rectangle, and 15% for diagonal, herringbone or chevron patterns where every perimeter tile is cut at an angle. Go to 20% for rooms with curves or many corners, and lean high with large-format tile, where a narrow cut wastes most of the tile.
How many 12x12 tiles do I need for 100 sq ft?
With 10% waste, 110 tiles. Since 12 × 12 in tile is exactly 1 sq ft each, the tile count and the square footage are the same number before waste is added, which makes it the easiest format to estimate.
How many square feet are in a box of tile?
Commonly 15 sq ft, which is what this calculator assumes, but it is not standard. Mosaic sheets and large-format tile often come 8 to 12 sq ft per box. Check the actual box quantity before ordering — boxes are not broken, so rounding up can add several square feet.
Why does tile from the same order look different?
Tile is fired in batches and color varies between them. Buy the whole job at once and check that every box carries the same lot number. A box from a different lot opened halfway across a floor shows under raking light, and the only fix is to pull up finished work.