How this tile calculator works
Tiling is sold by quantity, so the job is to work out how many tiles cover your floor or wall. The principle is simple: tiles needed = surface area ÷ the area of one tile, rounded up. First find the area you are covering by multiplying its length by its width. Then find the area of a single tile by multiplying the tile width by its height. Dividing one by the other gives the bare number of tiles, before any allowance for cuts.
Two refinements make the estimate more realistic. First, the grout gap: each tile sits in a grid where it occupies its own size plus the joint width, so including the gap makes each tile effectively cover a little more and you need marginally fewer. Second, the waste allowance: edge tiles must be cut, the offcuts are usually too small to reuse, and the odd tile breaks — so you add a percentage (typically 10%, more for diagonal or herringbone layouts) and round up. If you know how many tiles are in a box, divide the total by that figure and round up to get boxes.
Reference note: results are a planning estimate. Layout, pattern, the number of doorways and obstacles, and how much you can salvage from offcuts all change real waste. Measure carefully, split irregular rooms into rectangles, add a sensible waste allowance, and confirm coverage on the tile packaging before buying.
Frequently asked questions
- How many tiles do I need?
- Divide the surface area you are covering by the area of a single tile, then round up. That is the floor or wall area divided by the area of one tile, plus a waste allowance for cuts and breakages. Enter your room and tile dimensions above and the calculator returns the count both before and after waste.
- How much extra or waste should I buy?
- About 10 percent is standard for a simple rectangular room laid straight. Add more — around 15 percent for diagonal layouts and 20 percent for herringbone or rooms with lots of obstacles — because every cut wastes part of a tile and you want spares for future repairs.
- Does grout spacing matter?
- A little. Each tile occupies its own size plus half a grout joint on every side, so a wider joint means each tile effectively covers slightly more area and you need marginally fewer tiles. The effect is small for thin joints but adds up over a large floor, so you can include the gap above.
- How do I calculate the area to tile?
- For a rectangular floor or wall, multiply the length by the width. Measure in the same unit, or let the calculator convert feet and inches or metres and centimetres for you. For an irregular space, split it into rectangles, work out each area and add them together.
- What about cuts and edges?
- Tiles along the edges almost always need cutting, and the offcuts are usually too small to reuse, so they count as waste. Complex and diagonal patterns waste more. That is exactly why you add a waste percentage rather than buying the bare calculated number of tiles.
- How many tiles come in a box?
- It varies by tile size and brand — large-format tiles may be a few to a box while small tiles can be dozens. The box label states the tile count and area it covers. Enter the tiles-per-box figure and the calculator divides your total by it and rounds up to tell you how many boxes to buy.