Why should I order extra tiles?

Tiles crack during installation, cuts create offcuts that cannot be reused, and you should keep a few spares for future repairs. The batch dye lot may not match if you reorder later.

What waste percentage should I use?

Use 10% for straight grid layouts. Use 15% for diagonal or herringbone patterns due to more cuts. Use 20% for irregular rooms with lots of cuts around fixtures.

How do I measure a bathroom with an irregular shape?

Break the floor into rectangular sections, calculate each separately, and add the totals.

How do I convert tile size from inches to cm?

Multiply inches by 2.54. A 12-inch tile = 30.48 cm. A 6-inch tile = 15.24 cm.

Do I need the same number of tiles for walls and floors?

The formula is the same. Only the area and waste factor differ. Walls often have more cuts around fittings, so increase the waste buffer to 15 to 20% for wall tiling.

What if tiles come in packs?

Divide the total tile count by the number of tiles per pack, then round up to the nearest whole pack.

Tile Calculator

Room Length

Room Width

Tile Length

Tile Width

Waste Allowance

10% standard; 15% for diagonal patterns

Formula

Tiles = (Room Area / Tile Area) × (1 + waste%/100)

Room area in m² divided by tile area in m² gives base tile count. Add waste percentage for cuts, breakages, and future repairs.

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TL;DR

Enter room dimensions and tile size to get the total number of tiles needed, including a waste buffer.

Enter your room dimensions and tile size to find out how many tiles to buy. Includes a 10% waste allowance for cuts, breakages, and pattern offsets. Returns tile count and total area. Buy 10-15% extra if you are laying on a diagonal.

Buying too few tiles mid-project is a real problem: the same batch may not be available later. Buying too many wastes money. This calculator gives you the right count with a waste buffer for cuts, breakages, and future repairs.

You came here because

Common situations

Bathroom floor tiling: Calculate tiles for a bathroom floor before visiting the tile shop.
Kitchen backsplash: Estimate tiles for a wall area, with extra for cuts around outlets and cabinets.
Outdoor patio: Scale up for large outdoor areas with larger format tiles.
Contractor quotes: Prepare accurate material lists for tiling job estimates.

Under the hood

How the calculation works

1Enter the room length and width in meters.
2Enter the tile size in centimeters.
3Set the waste percentage: 10% for straight layouts, 15% for diagonal patterns.
4The calculator computes room area, divides by tile area, and rounds up to a whole number.
5The waste buffer is added on top of the base count.

Show me

A real example

Example: 5m × 4m room with 30×30 cm tiles, 10% waste

1Room area = 5 × 4 = 20 m²
2Tile area = 0.30 × 0.30 = 0.09 m²
3Base tiles = 20 / 0.09 = 222.2 → 223 tiles
4Waste buffer = 223 × 10% = 22.3 → 23 tiles
5Total = 223 + 23 = 246 tiles

Result: 246 tiles needed for 20 m² with 10% waste allowance

Watch out for

What can go wrong

Not adding enough waste: The default 10% waste covers straight layouts. A diagonal or herringbone pattern can waste 15-20% of tiles in cuts. Increase the waste buffer before ordering for complex patterns.
Measuring the total floor area including fixtures: Measure the net floor area where tiles will be laid, not the gross room dimensions. Subtract the footprint of fixed cabinets, bathtubs, and toilet bases.
Ordering in one batch but installing in phases: If you buy tiles in phases, you risk batch mismatches. Tiles from different batches have slight colour variation. Order all tiles for a room at once, even if you install over multiple days.
Confusing tile size with tile face size: A "300 mm tile" refers to its face dimension. Installed with 3 mm grout joints, the effective laid size is 303 mm. For large areas with many tiles, this small difference changes the total count.

Glossary

Related concepts

Term	Definition
Waste factor	Extra tiles ordered beyond the measured requirement to account for cuts, breakages, and future repairs. Typically 10–15%.
Grout lines	The gaps between tiles filled with grout. They reduce the effective tile coverage slightly. For most calculations, this is negligible.
Diagonal laying	Setting tiles at 45° creates a different visual effect but increases waste due to more cuts. Add 15% waste for diagonal patterns.
Rectified tiles	Precisely machine-cut tiles with uniform dimensions, allowing tighter grout joints (2–3 mm instead of 5+ mm).

Make it better

Pro tips

Add 15-20% for diagonal and pattern layouts: Change the waste percentage in the calculator to 15 or 20 for diagonal, herringbone, or chevron patterns. The extra cuts generate significantly more waste than a straight grid.
Sketch the layout before ordering: Mark where full tiles, half tiles, and cut tiles fall in your space. This tells you whether you need large or small cuts at the perimeter, which affects how much waste to allow.
Keep 5-10 tiles after completion: Store spare tiles from the same batch. Tiles crack, chip, or stain, and matching a discontinued tile years later is extremely difficult. A small reserve saves a future repair job.
Calculate grout separately: Grout quantity depends on tile size, grout joint width, and grout depth. Use the grout manufacturer's coverage tables rather than estimating, one bag of grout covers very different areas depending on tile size.

Common questions

Frequently asked questions

For related calculations, try the Concrete Calculator, or Paint Calculator. Browse all Calculator Online calculators for the full catalog.

Methodology

This calculator uses the standard tile calculator formula. Results match those from established financial, scientific, and health references.

Reviewed by

Calculator Online Editorial Team. All formulas verified against authoritative sources before publication.

Last updated

2026-01-15