# Floor Tile Waste Calculator

> Work out how many floor tiles and boxes to buy from the room size, tile size and joint width, with a waste allowance for cuts and breakage.

Category: Construction · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/floor-tile-waste-calculator

Divide the floor area by the area of one tile plus its joint, then add a waste allowance for cuts, breakage and spares, and round up to whole boxes.

Also called: Tile quantity calculator, Flooring tile estimator.

## Inputs
- Units (options: Metric, Imperial; default metric)
- Floor length (default 4)
- Floor width (default 3)
- Tile length (default 300)
- Tile width (default 300)
- Joint width (default 3; optional)
- Waste allowance (unit %; default 10; optional)
- Tiles per box (default 10; optional)

## Results
- Tiles to buy (with waste)
- Tiles to cover the floor
- Extra tiles for waste
- Boxes
- Floor area
- Floor area

## Formula

```
Tiles = ⌈L × W ÷ [(a + j)(b + j)] × (1 + Waste)⌉;  Boxes = ⌈Tiles ÷ Tiles per box⌉
```

Where:
- L, W: floor length and width
- a, b: tile length and width
- j: joint width

## Worked example
1. Floor = 4 × 3 = 12 m²; one tile = 0.3 × 0.3 = 0.09 m².
2. 12 ÷ 0.09 = 133.3 → 134 tiles to cover the floor.
3. With 10% waste: 133.3 × 1.1 = 146.7 → 147 tiles = 15 boxes of 10.

**Result:** A 4 × 3 m floor in 300 mm tiles needs 147 tiles (15 boxes) with a 10% allowance.

## What the result means

Buy all tiles from one batch (shade and calibre), and keep a few spares for future repairs. Large-format tiles and diagonal layouts waste more at the edges.

## Assumptions and limits
- A rectangular floor; split L-shaped rooms into rectangles and add them.
- Does not plan cuts; a layout drawing can reduce waste for expensive tiles.

## Questions

### How much tile waste should I allow?

Commonly about 10% for a straight lay in a simple room and 15–20% for diagonal, herringbone or rooms with many corners.

### Does the grout joint matter?

Slightly: a 3 mm joint on 300 mm tiles saves about 2% of tiles. It matters more for small tiles and mosaics.

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_Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/floor-tile-waste-calculator