How much extra tile should I buy?

A common guide is 10% extra for straight or brick layouts, 15% for diagonal and 30% for herringbone, to cover cuts and breakages. Keep a few spare tiles from the same batch for repairs.

Why is the laid-out count higher than the tiles to buy?

The laid-out count treats every cut tile as a whole tile with the offcut thrown away. On a real job most offcuts get used on the opposite edge. With large tiles in a small room, offcuts often don't fit anywhere else, so lean toward the laid-out number.

Does the grout joint change how many tiles I need?

Yes, a little. Each tile takes up its own size plus one joint, so wider joints mean slightly fewer tiles per square metre. With 600 mm tiles a 3 mm joint makes about a 1% difference.

How much grout do I need?

Grout depends on the joint, not just the area: kg per m² = ((length + width) × thickness × joint) ÷ (length × width) × about 2 for a cement grout. For 600 × 600 × 10 mm tiles with 3 mm joints that's 0.2 kg per m², plus 15% wastage. Small tiles and wide joints use much more.

Can I lay square tiles in herringbone?

Not really. Herringbone needs planks at least twice as long as they are wide, so the tiles interlock. Use a straight, brick or diagonal layout for square tiles.

Free calculator

Tile calculator

Tiles = area × tiles per m² × (1 + wastage). Tiles per m² = 1 ÷ ((tile length + joint) × (tile width + joint)). Allow 10% wastage for straight or brick layouts, 15% for diagonal and 30% for herringbone.

Your job

What are you tiling?

Length

Width

L-shaped room? Split it into two rectangles.

Tile and layout

Tile length

Tile width

Joint

Pattern

Wastage allowance10%

Set by the pattern (10% straight or brick, 15% diagonal, 30% herringbone). Covers cuts and breakages.

Grout and adhesive

Tile thickness

Grout factor

Add the thickness to get grout in kg. The factor is about 2 for a cement-based grout; epoxy and lightweight grouts differ, so check the bag.

Adhesive bag covers

Coverage changes with the product and the trowel notch, so read it off the bag.

Boxes and look

Tiles per box

Every range boxes differently, so read it off the label or the product page.

Finish

Highlight cut tiles

Optional

Your price per m²

Ask your tile supplier. The greyed number is an example only and is never used in your result.

Drawn to scale. Striped tiles are cut at the edges.

Tiles to buy

28tiles

Add tiles per box to get boxes

Area

9.25m²

1 area

Laid out

35tiles

24 full + 11 cut, no offcuts reused

Tiles per m²

2.75

600 × 600 mm with 3 mm joints

The working, with your numbers

1. Area3.7×2.5= 9.25 m²
2. Tiles per m²1 ÷ (0.603 × 0.603)= 2.75
3. Tiles9.25 × 2.75 × 1.10, rounded up= 28

Typed those measurements in by hand?MetreMate measures them straight off your PDF plans. Free to start.

The formula, in plain words

1Area = length × width for each floor or wall, added together. Split an L-shaped room into rectangles.
2Tiles per m² = 1 ÷ ((tile length + joint) × (tile width + joint)), all in metres.
3Tiles = area × tiles per m² × (1 + wastage), rounded up. Wastage covers cuts and breakages: 10% straight or brick, 15% diagonal, 30% herringbone.
4Boxes = tiles ÷ tiles per box from the label, rounded up.
5Grout kg per m² = ((tile length + tile width) × joint depth × joint width) ÷ (tile length × tile width) × a density factor (about 2 for cement grout), all in mm. Joint depth is the tile thickness. Add 15% for wastage.
6Laid out: the pattern is drawn over each area and every tile that touches it is counted, full or cut. That is the most you'd use if no offcut is reused.

Worked example

A 3.7 × 2.5 m floor in 600 × 600 mm tiles with 3 mm joints, laid straight, 10% wastage.

1.Area: 3.7 × 2.5 = 9.25 m².
2.Tiles per m²: 1 ÷ (0.603 × 0.603) = 2.75.
3.Tiles: 9.25 × 2.75 × 1.1 = 27.98, rounded up to 28.
4.Laid out, the floor takes 24 full tiles and 11 cut ones. With big tiles in a small room, reuse offcuts or buy toward the laid-out count.

Answer: 28 tiles, plus the boxes to cover them. Laid out it's 24 full and 11 cut, 35 tiles if no offcut is reused.

How to measure it

Measure the length and width of each floor, or the length and height of each wall, in metres.
Split L-shaped or stepped rooms into rectangles and add each one.
Take the tile size and the joint width you'll use off the product or your spacers.
Read the tiles per box off the label so the result comes out in boxes.

Where the numbers come from

Every default in the calculator is a number a supplier or manufacturer publishes. We list the source next to it so you can check.

What	Value	Source
Wastage for straight (grid) and standard layouts	10 %	National Tiles, tile and flooring area calculator (waste allowance guide) (checked 2026-09-30)
Wastage for diagonal and complex layouts	15 %	National Tiles, tile and flooring area calculator (waste allowance guide) (checked 2026-09-30)
Wastage for herringbone and intricate layouts	30 %	National Tiles, tile and flooring area calculator (waste allowance guide) (checked 2026-09-30)
Grout density factor for a cement-based grout, in kg/m² = ((L + W) × depth × joint) ÷ (L × W) × factor	2 factor	ARDEX Australia, FG 8 grout calculator (formula and factor read from the product page) (checked 2026-09-30)
Grout wastage allowance	15 %	ARDEX Australia, FG 8 grout calculator (formula and factor read from the product page) (checked 2026-09-30)

Manufacturers named here are the source of the number, not a recommendation. Confirm quantities with your supplier.

Frequently asked questions

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