How many tiles do I need per square metre?

Divide 1 by the tile area in square metres (including the grout joint). For a 300x300mm tile with 3mm grout: tile cell = 0.303 x 0.303 = 0.0918 m2. Tiles per m2 = 1 / 0.0918 = 10.9, so approximately 11 tiles per square metre. For 600x600mm with 3mm grout: 0.603 x 0.603 = 0.3636 m2, so about 2.75 tiles per m2. This calculator shows tiles per square metre in the results.

How does grout joint size affect tile quantity?

The grout joint adds to the effective area of each tile. A 300x300mm tile with 3mm grout occupies 303x303mm of floor space rather than 300x300mm. This slightly reduces the number of tiles needed compared to calculating with tile dimensions alone. For 3mm grout, the difference is about 2% - small but it accumulates over large areas. This calculator includes grout joint size in its calculation.

How many tiles per square foot?

Divide 1 by the tile area in square feet. For a 12x12 inch tile with 1/8 inch grout: tile cell = 12.125 x 12.125 = 147.02 sq in = 1.021 sq ft. Tiles per sq ft = 1/1.021 = 0.98, essentially 1 tile per square foot. For 6x6 inch tiles: about 4 tiles per square foot. Switch this calculator to imperial mode and it will calculate tiles per square foot automatically.

Tile Calculator – Multiple Rooms, Waste & Cost (Free)

Q: How do I calculate how many tiles I need?

Measure the room length and width in metres or feet. Multiply to get the area. Divide the area by the area of one tile (including the grout joint). Add a wastage percentage (10% for straight lay, 15% for diagonal, 5-10% for simple rectangular rooms). Round up to the nearest whole tile. This calculator does all of this automatically, including deductions for obstacles like doors, islands and bathtubs.

Q: What wastage percentage should I use?

Use 10% for a standard straight lay in a regular rectangular room. Use 15% for diagonal or herringbone patterns, which require more cuts. Use 5% for very large tiles in a simple room (fewer cuts needed). Use 20% if there are many awkward corners, angles or obstacles. Always round up when in doubt - running out of tiles mid-project means ordering a new batch that may not match the dye lot of the original tiles.

Q: How many boxes of tiles do I need?

Divide the total tiles needed (including wastage) by the number of tiles per box, then round up to the nearest whole box. For example, 230 tiles needed at 10 per box = 23 boxes exactly. At 11 per box = ceil(230/11) = 21 boxes. Enter the tiles per box in this calculator and it will automatically calculate boxes needed.

Q: Should I buy extra tiles?

Yes, always buy slightly more than the calculator suggests. The wastage percentage covers cuts and breakages during installation. However, tiles are made in batches (dye lots) and colour can vary slightly between batches. If you need to replace a cracked tile in 5 years and the original batch is discontinued, matching tiles from a new batch may differ in shade. Store 5-10% extra from the same batch after installation.

Q: Tile calculator for bathroom free

Enter bathroom length and width. Add deductions for the bathtub and toilet cistern if needed. Enter tile size (select from presets or enter custom dimensions). Set wastage to 10-15% for bathroom tiles (which often have more cuts around fixtures). Enter tiles per box and price to get total cost. Metric and imperial both supported.

Tiling Guide

How to Calculate Tiles for a Room — Step by Step

Getting the tile quantity right before you order is one of the most important steps in any tiling project. Too few and you face the problem of matching a discontinued batch. Too many and you have wasted money. Here is exactly how this calculator works — and how to get the most accurate result.

Step 1 — Measure the room correctly

Measure the length and width of the floor or wall area in metres (or feet if using imperial mode). For a floor, measure wall to wall at the longest points. For walls, measure height and width of each wall section. If the room is L-shaped, calculate it as two rectangles and add both as separate rooms in the calculator. Always measure in multiple places — rooms are rarely perfectly rectangular. Use the longest dimension to be safe.

Step 2 — Subtract obstacles and deductions

Do not subtract doorways from a floor calculation — tiles are usually cut across doorways and the threshold tile is counted in the main area. Do subtract large fixed obstacles such as kitchen islands, bath panels, shower trays and built-in furniture bases where no tiling occurs. Enter each deduction as a length and width pair using the “Add deduction” button. The calculator subtracts these from the gross room area automatically.

Step 3 — Choose the right wastage percentage

Wastage accounts for cut pieces, breakages and the off-cuts discarded when fitting around edges, corners and obstacles. The standard rule of thumb is 10% for a straightforward rectangular room with a simple grid lay. Use 15% for diagonal patterns (tiles laid at 45 degrees), which waste more material at the edges. Use 15–20% for herringbone or basket-weave patterns. Use 5% for very large tiles (e.g. 1200×1200mm) in a clean rectangular room, since there are fewer cuts proportionally. Add an extra 5% if the room has many recesses, angled walls or complex shapes.

Step 4 — Account for grout joints

Grout joints are the gaps between tiles filled with grout. They are part of the floor area but not part of the tile itself. Standard grout joints are 2–3mm for wall tiles and 3–5mm for floor tiles. Rectified tiles (precision-cut with straight edges) are often laid with 1.5–2mm joints. The calculator adds the grout joint to each tile dimension before computing area per tile, which gives a more accurate result than calculating from tile dimensions alone. For most projects the difference is small, but it becomes meaningful over large areas or with wide grout joints.

Step 5 — Calculate boxes and round up

Tiles are sold in boxes. Enter the tiles per box from the product specification on the shop listing or tile packaging. The calculator divides total tiles needed by tiles per box and rounds up to the nearest whole box — you cannot buy a partial box. Enter the price per box to get a total material cost estimate. This does not include adhesive, grout, tools or installation labour.

Wastage Guide

Tile Wastage: How Much Extra Do You Really Need?

📐

10% — standard for most projects — A 10% wastage allowance is right for a rectangular or near-rectangular room laid in a straight grid pattern. This covers normal edge cuts (tiles against walls are cut to fit), an average number of breakages, and a small reserve. If you are an experienced tiler who rarely breaks tiles, 8% may be sufficient. If you are tiling for the first time, 12% gives more comfort.

📐

15% — for diagonal patterns and irregular rooms — Diagonal patterns (tiles at 45 degrees) waste significantly more material because every perimeter tile must be cut at an angle. The off-cut triangles are rarely usable elsewhere. Similarly, rooms with many internal corners, recesses or non-parallel walls generate more waste cuts than simple rectangles. Use 15% as a minimum for these situations.

⚠️

20%+ — for complex patterns and highly irregular spaces — Herringbone, basketweave, Versailles and other multi-direction patterns can waste 15–25% of material. Similarly, tiling bathrooms with many plumbing fixtures to cut around, or oddly shaped spaces with angled walls, can push wastage higher. When in doubt, set 20% — the extra boxes can always be stored for future repairs and matching later is difficult once the batch is discontinued.

💡

The dye lot problem — why you should always over-order slightly — Ceramic and porcelain tiles are manufactured in batches. Even within the same product range, two boxes from different production runs (different “dye lots”) can vary subtly in colour, shade, or surface texture. Once a particular batch is sold out, the shop may stock a new batch that is visibly different when placed next to the original. If you run short mid-project and need to order more tiles, you may not be able to match your existing floor or wall. Always err on the side of buying one extra box — store it in case of future repairs.

Comparison

LazyTools vs Other Tile Calculators

Feature	LazyTools	HomeDepot	Tile.co.uk	Omnicalculator
Multiple rooms	✅ Yes	❌ One room	❌ One room	❌ One room
Deductions for obstacles	✅ Yes (per room)	❌ No	❌ No	⚠ Limited
Grout joint size	✅ Yes (mm)	❌ No	✅ Yes	✅ Yes
Adjustable wastage %	✅ Yes (5–30%)	⚠ Fixed 10%	⚠ Fixed	✅ Yes
Boxes + cost estimate	✅ Yes	✅ Yes	✅ Yes	⚠ Boxes only
Metric and imperial	✅ Both	⚠ Imperial only	⚠ Metric only	✅ Both
17 tile size presets	✅ Yes	❌ No	⚠ Some	⚠ Few

Reference

Tiles Per Square Metre — Quick Reference

Tile size	Grout (3mm)	Tiles/m²	Tiles/ft²
100×100mm	103×103mm cell	94.2	8.75
150×150mm	153×153mm cell	42.7	3.97
200×200mm	203×203mm cell	24.3	2.26
300×300mm	303×303mm cell	10.9	1.01
300×600mm	303×603mm cell	5.47	0.51
450×450mm	453×453mm cell	4.87	0.45
600×600mm	603×603mm cell	2.75	0.26
600×1200mm	603×1203mm cell	1.38	0.13

FAQ

Frequently Asked Questions

How do I calculate how many tiles I need?▾

Measure room length and width. Multiply for gross area. Subtract any obstacles. Divide by tile area (tile + grout joint). Add wastage (10% standard). Round up. Enter your dimensions in the calculator above for an automatic result.

What wastage percentage should I use?▾

10% for a standard rectangular room with straight grid pattern. 15% for diagonal pattern, irregular rooms, or many obstacles. 20% for complex patterns (herringbone, basketweave). 5% for very large tiles in simple rooms. When in doubt, add an extra box.

How many tiles per square metre?▾

Divide 1 by the tile cell area (tile + grout joint) in m2. 300x300mm with 3mm grout = 10.9 tiles/m2. 600x600mm = 2.75 tiles/m2. See the reference table above for all common sizes. The calculator shows tiles per m2 (or ft2) in its results.

How many boxes of tiles do I need?▾

Total tiles needed (with wastage) divided by tiles per box, rounded up to the nearest whole box. Enter tiles per box in the calculator above and it calculates this automatically.

Tile calculator for bathroom free▾

Enter bathroom length and width, add deductions for bathtub or shower tray, set tile size and 10-15% wastage. Add tiles per box and price for cost. Works for floor tiles and wall tiles. Free, no account, no ads.

Does grout joint size affect tile quantity?▾

Yes. Grout joints are part of the floor area. Adding 3mm to each tile dimension before computing area gives a more accurate result than using tile dimensions alone. For 300x300mm with 3mm grout, each tile occupies 303x303mm = 0.0918m2 rather than 0.09m2 - a 2% difference that adds up over large areas.

Floor tile calculator in square feet▾

Switch the calculator to Imperial mode using the toggle at the top. Enter room dimensions in feet. Select a tile size in inches from the presets (4x4, 6x6, 12x12, 12x24, 18x18, 24x24 inch) or enter custom mm dimensions. Results shown in square feet and tiles per square foot.

Should I buy extra tiles?▾

Yes. Always buy at least one extra box from the same batch. Tiles from different production runs can vary in shade or texture. If a tile cracks in 5 years and you need a replacement, matching the original batch after it is discontinued is often impossible. Store leftover tiles from the same batch after installation.

Related tools