Calculate tile quantity from the surface area, tile size, layout, grout joints and a practical allowance for cuts and breakage.
The basic tile calculation is simple, but buying the exact number obtained from a calculator can leave you short once tiles have to be cut around walls, corners, doors, fixtures or unusual room shapes.
A reliable estimate therefore combines surface area with tile dimensions and a suitable waste allowance. For wall tiling, openings such as doors and windows should also be considered.
Tile Quantity Formula
For a rectangular floor or wall, the calculation can be broken into three main steps.
Area = Length x Width
Tile coverage:
Tile Area = Tile Length x Tile Width
Number of tiles:
Tiles Needed = Surface Area ÷ Tile Area
The result should then be increased to account for cuts, breakage and the particular installation pattern.
Order Quantity = Calculated Tiles x (1 + Waste Allowance)
Step 1: Measure the Area to Be Tiled
For a rectangular floor, measure the length and width.
Floor Area = Length x Width
For example, a floor measuring 6 m by 4 m has an area of:
If the area is not rectangular, divide it into smaller rectangles or other simple shapes, calculate each section and add the results together.
How to Calculate Wall Tile Area
For a rectangular wall, multiply its width by its height.
Wall Tile Area = Wall Width x Wall Height
If a wall contains a door, window or another opening that will not be tiled, calculate that opening separately and subtract it.
Net Wall Area = Gross Wall Area - Opening Area
For several walls, calculate each wall and combine the net areas.
Step 2: Calculate the Area of One Tile
Tile dimensions are often given in millimetres or centimetres, while room dimensions may be measured in metres. Convert the tile dimensions to metres before calculating square metres.
| Tile size | Tile dimensions in metres | Area per tile |
|---|---|---|
| 300 x 300 mm | 0.30 x 0.30 m | 0.09 m² |
| 400 x 400 mm | 0.40 x 0.40 m | 0.16 m² |
| 600 x 600 mm | 0.60 x 0.60 m | 0.36 m² |
| 600 x 1200 mm | 0.60 x 1.20 m | 0.72 m² |
The tile area is calculated by multiplying its length by its width.
Step 3: Divide Surface Area by Tile Area
Once the surface area and individual tile area are known, divide the first by the second.
For a 24 m² floor using 600 x 600 mm tiles:
One Tile = 0.60 x 0.60 = 0.36 m²
24 ÷ 0.36 = 66.67 tiles
Because tiles are purchased as whole pieces, the calculated quantity must be rounded up before applying the practical allowance.
In this example, the basic requirement is approximately 67 tiles.
Why You Need Extra Tiles
The mathematical result assumes every tile can be used perfectly with no cuts or breakage. Real installations rarely work that way.
Extra tiles can be needed for:
- Edge cuts
- Corner cuts
- Door openings
- Columns and projections
- Irregular room shapes
- Broken tiles
- Pattern alignment
- Future repairs
The required allowance depends on the project rather than one universal percentage.
How Much Tile Waste Should You Allow?
A small, simple rectangular room with a straightforward layout may need less extra material than a room with many corners, angles or detailed patterns.
For a basic illustration, suppose you decide to use a 10% allowance on the 67-tile example:
67 x 1.10 = 73.7 tiles
Round the purchasing quantity up to a whole tile, giving approximately 74 tiles.
Worked Example: Floor Tiles
Consider a rectangular floor measuring 5 m by 4 m. The selected tile is 600 x 600 mm.
1. Calculate floor area
5 x 4 = 20 m²
2. Calculate one tile's area
0.60 x 0.60 = 0.36 m²
3. Calculate the basic tile quantity
20 ÷ 0.36 = 55.56 tiles
Round up:
56 tiles
4. Add an example 10% allowance
56 x 1.10 = 61.6 tiles
The practical purchasing quantity would therefore be at least 62 tiles under this example assumption.
How to Calculate Tiles for Multiple Rooms
For several rooms, you can calculate each room separately or calculate the combined area if the same tile and installation conditions apply.
Calculating rooms separately is often easier to check, especially when rooms have different shapes or require different tile patterns.
Room A = 12 m²
Room B = 18 m²
Total area = 30 m²
If the same tile is used throughout, the 30 m² can then be used for the basic tile calculation.
Tiles Per Square Metre
Another useful way to estimate tile quantity is to calculate how many tiles fit into one square metre.
Tiles per m² = 1 ÷ Tile Area
For a 600 x 600 mm tile:
1 ÷ 0.36 = 2.78 tiles per m²
That figure can then be multiplied by the total tiled area.
Total Tiles = Area x Tiles per m²
This produces the same mathematical result as dividing the total area by the area of one tile.
How Grout Joints Affect Tile Calculations
Tiles are normally installed with joints between them. For many basic area calculations, tile coverage is based on the tile's physical dimensions, while the exact layout determines how many full and cut pieces are required.
For a precise installation plan, the grout joint width should be considered alongside tile dimensions, room dimensions and the selected layout.
This becomes particularly important when the tiles are large, the room has tight dimensions or the layout needs a specific centreline or pattern.
Large Tiles and Cutting Loss
Large-format tiles cover more area per piece, but that does not automatically mean less cutting waste.
A room with several narrow edges can produce substantial offcuts. Some offcuts can be reused elsewhere, while others may not fit another section of the installation.
For large-format or detailed layouts, the tile quantity should therefore be checked against the actual layout rather than relying only on an area calculation.
Tiles Sold by Box
Tiles are often sold in boxes containing a specified number of tiles or a specified coverage in square metres.
If the box coverage is known, you can calculate the number of boxes directly:
Boxes Needed = Required Tile Area ÷ Coverage per Box
Always round the number of boxes up to a whole box.
A project requires 24 m² after the selected allowance, while one box covers 1.44 m².
24 ÷ 1.44 = 16.67 boxes
The purchase quantity would therefore be 17 boxes.
Calculating Tiles for Walls With Openings
Wall tile calculations follow the same basic area method, but doors and windows can make a noticeable difference.
For example, if a wall measures 5 m wide by 2.8 m high:
5 x 2.8 = 14 m²
If a 0.9 m x 2.1 m door occupies part of that wall:
0.9 x 2.1 = 1.89 m²
14 - 1.89 = 12.11 m²
The tile quantity can then be calculated from the 12.11 m² net surface.
Diagonal and Patterned Tile Layouts
Straight layouts are usually easier to estimate because tiles follow the main dimensions of the room. Diagonal layouts, staggered patterns, borders and decorative designs can create more offcuts.
The area calculation remains useful for establishing the base quantity, but the allowance should reflect the actual layout.
For a complicated pattern, a tile layout plan can provide a more precise estimate than an area-only calculation.
Common Tile Calculation Mistakes
Using centimetres without conversion
If the room is measured in metres but tile dimensions are entered as centimetres, the area calculation can be off by a large factor. Convert the units before calculating.
Forgetting wall openings
Doors and windows should be considered when estimating wall tile quantities if those areas will not receive tiles.
Buying the exact mathematical quantity
The theoretical result does not account for cuts, breakage or future repairs. A practical allowance is important.
Rounding down
You cannot purchase a fraction of a tile or box. Round the required purchasing quantity up.
Ignoring the box coverage
If tiles are sold by box, calculate the required number of boxes rather than stopping at the individual tile count.
Assuming waste is always the same
A simple rectangular room and a complex patterned installation can have very different cutting requirements.
Tile Quantity Checklist
- Measure the floor or wall.
- Calculate the total surface area.
- Subtract doors and windows where applicable.
- Check the tile dimensions.
- Convert all measurements to compatible units.
- Calculate the area covered by one tile.
- Divide total area by tile area.
- Round the basic quantity up.
- Allow for cuts and breakage.
- Check the tile coverage per box.
- Round the final box quantity up.
Use the BuildersMeasures Tile Calculator
For a quicker calculation, use the BuildersMeasures Tile Calculator to estimate the quantity required from your project measurements.
If you are working with wall tiles, the Wall Area Calculator can help determine the surface area first.
Calculate tile quantities. Flooring Calculator
Calculate flooring areas and quantities. Wall Area Calculator
Calculate wall surface area. Walls, Flooring & Finishes
Browse related construction tools.
Frequently Asked Questions
How do I calculate how many tiles I need?
Calculate the area to be tiled, calculate the area covered by one tile, divide the surface area by the tile area and add a practical allowance for cuts and breakage.
How many 600 x 600 mm tiles do I need for 20 m²?
Each 600 x 600 mm tile covers 0.36 m². Dividing 20 m² by 0.36 gives approximately 55.56 tiles, so the basic quantity is 56 tiles before adding an allowance.
Should I subtract doors and windows when calculating wall tiles?
Yes. If those openings will not be tiled, calculate their area and subtract it from the gross wall area.
How much extra tile should I buy?
The appropriate allowance depends on the room shape, tile size, layout, pattern, cutting requirements and expected breakage. There is no single percentage that applies to every project.
How do I calculate the number of tile boxes needed?
Divide the required tiled area by the coverage provided by one box, then round the result up to the next whole box.
Do grout joints change the number of tiles I need?
Grout joints affect the actual layout and spacing of tiles. For detailed layouts, joint width should be considered alongside tile dimensions and the room dimensions.
Final Tile Calculation
Tile Area = Tile Length x Tile Width
Basic Tile Quantity = Surface Area ÷ Tile Area
Final Order Quantity = Basic Quantity + Practical Allowance
The important part is to calculate the actual surface being tiled, use compatible units, and account for the cutting and installation conditions before placing the order.
For a faster estimate, use the Tile Calculator or explore the Walls, Flooring & Finishes Calculators hub for related tools.