Short answer
A 3 x 2.5 m floor (7.5 m²) in 600 x 600 mm porcelain tiles with a 2 mm joint and 10% spare needs 23 tiles, which is 6 boxes of 1.44 m². Allow 2 bags of adhesive with a 12 mm trowel and 1 x 5 kg bag of grout. Materials come to about $427 to $991, or roughly $675 to $1,575 if a tiler lays it. The calculator below works for any size, joint and layout.
Use this free tile calculator to work out how many tiles and boxes you need for a floor or wall, plus the adhesive, grout and waterproofing membrane, and an indicative cost. Choose a tile size, set the grout joint and layout, and the quantities update as you go.
Tile calculator
Tile quantities are calculated from your sizes. Adhesive and grout coverage depends on the product, so use these as a guide and check the pack. Prices are indicative. Ranges reviewed October 2026.
How to calculate how many tiles you need
- Area: length x width of the surface in metres, less doors and windows on walls.
- Tiles per square metre: 1,000,000 ÷ ((tile length + joint) x (tile width + joint)), with sizes in millimetres. A 600 x 600 mm tile with a 2 mm joint gives about 2.8 tiles per m².
- Spare allowance: add 10% for a straight lay, then round up to whole boxes.
- Boxes: area with spare ÷ coverage per box, rounded up. Box sizes vary by brand, so check the pack.
| Example | Tiles | Boxes | Adhesive (20 kg) | Grout |
|---|---|---|---|---|
| Floor 3 x 2.5 m, 600 x 600 mm, 2 mm joint, 10% | 23 | 6 x 1.44 m² | 2 bags (12 mm notch) | 0.9 kg |
| 10 m² of 600 x 600 mm, 2 mm joint, 10% | 31 | 8 x 1.44 m² | 2 to 3 bags | 1.2 kg |
| 12 m² of 300 x 600 mm, 2 mm joint, 10% | 73 | 11 x 1.26 m² | 2 to 3 bags (10 mm notch) | 2.2 kg |
| 4 m² splashback, 75 x 150 mm subway, 2 mm joint, 10% | 376 | by pack | 1 to 1 bags (6 mm notch) | 2.3 kg |
How much spare should you buy?
- Straight lay: about 10%. Beaumont’s own calculator adds 10%.
- Diagonal, large format and small rooms: about 15%. Tile Cloud treats 15% as standard and suggests 10 to 15% in its guidance.
- Herringbone: about 20%.
- Same batch: buy everything in one order so the shade and size match, and keep a box or a few tiles for repairs.
Grout joint widths
Follow the manufacturer’s recommendation for your tile. As a guide, retailers suggest 1.5 to 2.5 mm for rectified tiles and 2.5 to 5 mm for non-rectified or cushion-edged tiles, and Mapei says current standards want at least 2 mm. A tiling guide citing the older AS 3958.1 recommends 3 mm for dust-pressed floor tiles and 1.5 mm for wall tiles. The Australian standard has since been revised as AS 3958:2023, so check the current edition or ask your tiler. Wider joints suit larger or irregular tiles, and consistent joints matter more than the exact width.
Adhesive and trowel sizes
Match the notch to the tile. Davco’s guide suggests 6 mm for mosaics and tiles up to 150 mm, 10 mm for larger tiles and 12 mm for tiles 400 x 400 mm and over, with back-buttering for large tiles or ribbed backs. Aim for 90 to 100% adhesive coverage behind the tile.
| Trowel notch | Coverage per 20 kg bag (calculator range) | What manufacturers say |
|---|---|---|
| 6 mm | 6 to 12 m² | Davco claims up to about 12 m² for Ultraflex; a Singapore sheet for the same product gives about 5 m² per 20 kg |
| 10 mm | 5 to 7 m² | Bostik data sheets give about 7 m² per 20 kg |
| 12 mm | 4 to 6 m² | Ardex Quickbond is listed at about 6.5 m² for floors; larger notches cover less |
A 20 kg bag of Davco adhesive costs about $23 to $35 at Bunnings, and Mapei Keraflex Maxi is about $45 to $67. Coverage depends on the product, the tile back and your technique, so read the bag, and when in doubt buy a spare.
How much grout do you need?
The formula is (tile length + width) ÷ (length x width) x joint width x tile thickness x about 1.8 kg per litre, per square metre, plus about 15% waste. Grout comes in bags such as 1.5, 5, 10, 15 and 20 kg from Davco and 5 kg from Mapei, with a 5 kg bag around $27 to $37. Mapei says a 5 kg bag of Ultracolor Plus covers about 15 m² of 200 x 200 x 10 mm tile, as a guide only.
Waterproofing, slip ratings and movement joints
- Waterproofing: under NCC 2022 Specification 26, shower floors (including any hob or step-down) must be waterproof, and shower walls must be waterproof to at least 1,800 mm above the floor. AS 3740 gives the installation detail. The Davco K10 Plus data sheet specifies two coats at about 1.5 L per m² (about 13 m² per 20 L pail), with a flood test after 3 days, while Mapei’s AquaDefense uses about 1 kg per m² for two coats. Use bandage at wall and floor junctions.
- Who can do it: in NSW a contractor licence is required for residential waterproofing work over $5,000 (see NSW Fair Trading), Queensland has a QBCC waterproofing licence class, and for Victoria check with the Building and Plumbing Commission. Rules differ by state, so confirm before you hire or start.
- Slip resistance: bathroom and wet-area floor tiles are usually rated by the wet pendulum test in AS 4586, where P3 is 35 to 44 and P4 is 45 to 54. Tile Cloud advises P3 to P4 or higher for wet bathrooms. We could not confirm a general code requirement for house bathroom floors, so check with your tiler.
- Movement joints: HIA guidance on movement joints (AS 3958:2023) says joints should be at least 6 mm wide and no more than 4.5 m apart on internal floors over 9 m in a dimension (and in any dimension outdoors), with perimeter joints optional under 10 m² if tiles sit at least 3 mm from the wall.
- Curing: for its K10 membrane Davco allows 1 to 2 hours between coats and 6 to 8 hours before tiling. Davco suggests about 6 to 8 hours before grouting with Ultraflex adhesive and roughly 24 hours after laying for its grouts. A new sand-cement screed needs at least 24 hours (Sika), and rough concrete needs 7 days (Davco).
Tile and installation costs
Tiles at Australian retailers typically cost about $20 to $55 per m² for budget ceramic, $41 to $100 for mid-range porcelain and $85 to $110 or more for premium porcelain, with natural stone from about $150. For floors, published guides put the installed cost at about $60 to $145 per m² for ceramic, $90 to $210 for porcelain and $110 to $270 for large-format tiles. These come from lead-generation and contractor sites, which skew high, and they match the $91 to $210 per m² floor rate on our tiler rates page. For walls, the same guides put installed tiling at about $70 to $200 per m² (see that page for splashbacks and other jobs), and the bathroom cost calculator for a whole bathroom.
Common mistakes
- Not buying enough. Cuts and breakage need 10 to 20%, and a later batch may not match.
- Using the wrong trowel. Too small a notch leaves voids, and tiles crack or lift.
- Skipping back-buttering on big tiles. Large tiles need full coverage to avoid hollow spots.
- Grouting too soon. Wait for the adhesive to set as the product says.
- No movement joints. Large floors need them to prevent cracking.
- Ignoring slip rating in wet areas. Choose a suitable rating for bathroom floors.
- Cutting corners on waterproofing. Leaks are expensive to fix, and the work may need a licensed waterproofer.
Frequently asked questions
How many 600 x 600 mm tiles do I need for 10 m²?
With a 2 mm joint and 10% spare, about 31 tiles. Tiles usually come in boxes, and at 1.44 m² a box that is 8 boxes (32 tiles, 11.52 m²), so you finish with a few spare for repairs.
How much tile adhesive do I need per square metre?
It depends on the product and the trowel. Manufacturers quote anywhere from about 4 to 12 m² per 20 kg bag, with bigger notches covering less. As a guide, we use 6 to 12 m² per bag at a 6 mm notch, 5 to 7 m² at 10 mm and 4 to 6 m² at 12 mm, so a 7.5 m² floor with a 12 mm notch needs 2 bags. Check the bag, and buy a spare bag for large or uneven tiles.
How much grout do I need?
It depends on the joint width and tile size. The formula is (tile length + width) ÷ (length x width) x joint width x tile thickness x about 1.8 kg per litre, plus about 15% waste. For 600 x 600 x 9 mm tiles with a 2 mm joint that is about 0.11 kg per m², so a 7.5 m² floor needs 0.9 kg, which is one 5 kg bag. For 300 x 300 mm tiles at 3 mm it is about 0.32 kg per m².
How wide should grout joints be?
Follow the tile maker first. Retailers suggest 1.5 to 2.5 mm for rectified tiles and 2.5 to 5 mm for non-rectified or cushion-edged tiles, and Mapei says current standards want at least 2 mm. One tiling guide that cites the older AS 3958.1 recommends 3 mm for dust-pressed floor tiles and 1.5 mm for wall tiles.
What size trowel do I need?
Davco’s trowel guide suggests a 6 mm notch for mosaics and tiles up to 150 mm, a 10 mm notch for larger tiles and a 12 mm notch for tiles 400 x 400 mm and over. Large tiles and tiles with ribbed backs also need back-buttering, because you should aim for 90 to 100% adhesive coverage.
Do I need to waterproof before tiling a bathroom?
Yes for wet areas. Under the NCC, shower floors (including any hob or step-down) must be waterproof and shower walls waterproof to at least 1,800 mm above the floor, and AS 3740 gives the installation detail. Licensing differs by state: in NSW a contractor licence is required for residential waterproofing work over $5,000, Queensland has a QBCC waterproofing licence class, and in Victoria you should check with the Building and Plumbing Commission.
How many extra tiles should I buy?
About 10% for a straight lay and 15% for diagonal lays, large-format tiles and small rooms, and about 20% for herringbone. Buy everything in one order so the shade matches, and keep a few spare tiles for future repairs.
Related tools
- Tiler rates - hourly rates and typical job prices
- Materials calculator - floor, paint and wall tile quantities
- Bathroom renovation cost calculator - the whole bathroom
- Renovation quote comparator - paste tiling quotes for red-flag analysis
Related reading: Bathroom Tiling: Cost and the Value It Adds (2026) (what bathroom tiling costs and how much value it adds).
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