Tile Calculator
Calculate how many tiles you need for a room, accounting for waste factor.
How we calculate it
Tiles = ceil(Room area / Tile area × (1 + Waste factor)). Waste factor covers cuts and breakage. It is higher for a diagonal layout than a straight one, since diagonal cuts leave more unusable offcuts.
Understanding your estimate
Order too few tiles and you are back at the store mid-project, hoping the next box still matches the color lot you opened. Order too many and a stack of sealed boxes sits in the garage, sometimes past the return window. The formula behind this calculator is short: room area divided by tile area, times a waste factor, rounded up. The waste factor is where the real decision sits.
An 11 by 13 bedroom, tiled
Say you are tiling an 11 ft by 13 ft bedroom with 12 in by 12 in tile, laid straight, at the default 10% waste factor.
- Room area: 11 × 13 = 143 ft².
- Each tile: 12 in ÷ 12 = 1 ft per side, so one tile covers 1 ft².
- Raw count with no waste at all: 143 ÷ 1 = 143 tiles.
- Add the waste factor: 143 × 1.10 = 157.3.
- Round up to 158 tiles. A calculator that rounded 157.3 down to 157 would send you home three-tenths of a tile short, which on a real job means a full tile short.
Why straight and diagonal don't share a default
The waste factor defaults to 10% for a straight layout and 15% for a diagonal one, and that split lives entirely in the pattern toggle above the field, not in the formula itself. Pick a pattern and the field fills in with that number before you have touched anything. The calculation underneath never sees "straight" or "diagonal" at all, only whatever fraction ends up sitting in that field once you hit calculate. Diagonal cuts leave more unusable offcuts at the wall line than a straight run does, which is the entire reason the two presets differ. Type your own number over the preset and it wins; the calculator never quietly puts its default back.
Why the tile field asks for inches, not feet
Room length and width are entered in feet, or meters once you switch units. Tile size is entered in inches, or centimeters, even while the rest of the form stays in feet. Nobody buying a box of 12 by 12 tile thinks of it as a third of a foot; the number on the box is 12 inches, so that is the field it gets. The same call already shaped the depth field on the Concrete Calculator, where slab thickness is entered in inches even though length and width stay in feet. A room and the material covering it get measured the way people actually buy and talk about them, not the way the math would prefer.
Why this shares its formula with the Flooring Calculator
Tile and plank flooring solve the identical geometry problem underneath: how many rectangular pieces at a given size fit a rectangular room, plus a waste allowance, rounded up. When the Flooring Calculator needed that exact math, we did not retype it with a different variable name and a slightly different rounding rule by accident. Both calculators now call one shared function for the geometry, and each keeps its own vocabulary layered on top, tiles here, planks there, so the labels on screen still match what you are actually buying. A fix to that shared math only ever needs to happen in one place, not in two versions that quietly drifted apart from each other over time.
What this calculator doesn't handle
This only works for a rectangular room, one length and one width. An L-shaped bathroom, or a bedroom with a closet alcove cut into one wall, needs to be split into two rectangles and calculated separately, then added together by hand. That is a deliberate limit, not an oversight: the same minimal scope every calculator here starts with, one shape done correctly before a more complex one gets added.