Tile Calculator

A tile calculator turns the two classic DIY tiler mistakes, buying a stack of boxes you cannot return, and buying too few and having to abandon a Saturday morning to drive back to the trade counter for one more, into a 30-second calculation. Type the length and width of the room (or rooms) you are tiling, the size of the tile in centimetres or inches, your waste allowance, and either the box coverage in m² per box or the number of tiles per box; the calculator returns the number of tiles to buy, the number of boxes to buy, and, if you fill in the per-box cost field, the total material cost. The default 10% waste allowance is the standard TCNA Handbook 2024 recommendation for a straight grid layout on a rectangular room; brick-bond, diagonal, herringbone, and rooms with many cuts each push the waste allowance higher, and the calculator's waste slider accepts any value from 0 to 50%. Tiles are sold by the box in most countries, and the box coverage in m² printed on the side of the box is the single number you need to convert the "effective area" output into a count of boxes. Boxes are always rounded UP because you cannot buy a third of a tile.

The calculator accepts room dimensions in metres, centimetres, feet, or inches, and tile dimensions in centimetres or inches. All internal math normalises to square metres using exact international conversion factors, 1 inch = 0.0254 m and 1 foot = 0.3048 m exactly, both by the 1959 international yard and pound agreement adopted by NIST and the BIPM. Switching between metric and imperial therefore changes only the labels on the input fields, not the underlying calculation. The multi-room mode lets you add an arbitrary number of additional rooms (an en-suite and a main bathroom, say, or a kitchen plus a pantry) so the calculator sums the gross area across all rooms before applying the waste multiplier and rounding boxes up.

How to Use the Tile Calculator

1. Pick the room unit, metres (m), centimetres (cm), feet (ft), or inches (in). The default is metres, which is the natural unit for most of the world; US users typically pick feet.
2. Pick the tile unit, centimetres (cm) or inches (in). Millimetres is the universal tile-sizing unit in trade catalogues, but the field accepts whole centimetres or inches for simplicity. For an exact 600 × 600 mm tile, type "60" cm.
3. Enter the length and width of the room. For a 3 × 4 m bathroom, type 3 and 4 (with the unit set to metres). For a 10 × 12 ft US bathroom, type 10 and 12 with the unit set to feet.
4. Enter the tile length and tile width. For a standard 60 × 60 cm porcelain, type 60 and 60 (with the unit set to centimetres). For a 12 × 12 in US mosaic, type 12 and 12 with the unit set to inches.
5. Set the waste allowance (%). The default 10% is the TCNA recommendation for a straight grid on a rectangular room. Bump to 12 to 15% for a diagonal layout, 15 to 20% for herringbone, or 12 to 17% for cut-up rooms with many corners, alcoves, or fixed objects.
6. Pick the packaging mode. "Area per box" matches the convention on the side of every European tile box (the box says "covers 1.44 m²" or similar). "Tiles per box" matches the convention on the side of every US mosaic and small-format box (the box says "contains 12 tiles").
7. Type the box coverage (in m²/box, if you picked area-per-box) or tiles per box (if you picked tiles-per-box). A standard 600 × 600 mm porcelain box covers 1.44 m² (4 tiles of 0.36 m² each); a 30 × 30 cm ceramic box covers 1 m² (≈ 11 tiles); a 12 × 12 in US mosaic box covers 10 ft² (10 tiles of 1 ft² each).
8. Optional: type the cost per box in your local currency if you want the calculator to also output a total cost. Leave the field blank to hide the cost line.
9. Optional: tick "Add more rooms" to combine multiple rooms (a whole-house tile job, a bathroom plus en-suite, a kitchen plus pantry). Each additional room takes its own length, width, and unit inputs; the calculator sums the gross area across all rooms before applying the waste multiplier.
10. Read the order summary at the top of the result block, total tiles (rounded up), total boxes (rounded up), and (if cost provided) total cost. The read-out grid below shows the gross area, the area with waste, the tile area in m², the exact tile and box counts before rounding, the box coverage, and the per-box cost.

the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size runs entirely in the browser. For the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size, Inputs are not stored, not transmitted, and not associated with any account.

The Formulae

The closed-form formula that drives the result box is:

gross_m² = Σ (room_length × room_width) across all rooms, after unit-normalising each room's length and width to metres.

effective_m² = gross_m² × (1 + waste_fraction), where waste_fraction = waste_allowance% ÷ 100.

tile_m² = tile_length × tile_width, after unit-normalising both to metres.

tiles_exact = effective_m² ÷ tile_m², and tiles_to_buy = ⌈ tiles_exact ⌉ (ceiling, because you cannot buy a fraction of a tile).

boxes_exact (area-per-box mode) = effective_m² ÷ box_coverage_m², and boxes_to_buy = ⌈ boxes_exact �.

boxes_exact (tiles-per-box mode) = tiles_to_buy ÷ tiles_per_box, and boxes_to_buy = ⌈ boxes_exact ⌉.

total_cost (optional) = boxes_to_buy × cost_per_box.

Both directions work in any consistent unit. The unit-normalisation happens once, inside the calculation, using exact factors: 1 m × 1 m = 1 m², 1 ft × 1 ft = 0.09290304 m² (NIST SP 811, exact since 1959), 1 in × 1 in = 0.00064516 m² (NIST SP 811, exact since 1959), 1 cm × 1 cm = 0.0001 m² (exact, SI prefix). The waste allowance stacks multiplicatively on the gross area: a 10% waste is a 1.10× multiplier, a 15% waste is a 1.15× multiplier, and so on. Combining waste with a pattern multiplier (e.g. diagonal 1.15×) is left to the user because the TCNA convention is to quote waste inclusive of pattern overhead, bump the waste slider to 15% for a 10%-grid + diagonal layout.

Worked Examples

Example 1: 5 × 5 m bathroom floor, 30 × 30 cm ceramic tiles, 10% waste, 1 m²/box (≈ 11 tiles/box). Gross area = 5 × 5 = 25 m². Effective area = 25 × 1.10 = 27.5 m². Tile area = 0.30 × 0.30 = 0.09 m². Tiles = ⌈ 27.5 ÷ 0.09 ⌉ = � 305.56 ⌉ = 306 tiles. Boxes = ⌈ 27.5 ÷ 1 ⌉ = 28 boxes (or ⌈ 306 ÷ 11 ⌉ = 28 in tiles-per-box mode, the same number).

Example 2: 10 × 10 m open-plan kitchen, 60 × 60 cm porcelain tiles, 10% waste, 1.44 m²/box. Gross area = 10 × 10 = 100 m². Effective area = 100 × 1.10 = 110 m². Tile area = 0.60 × 0.60 = 0.36 m². Tiles = ⌈ 110 ÷ 0.36 ⌉ = � 305.56 ⌉ = 306 tiles. Boxes = ⌈ 110 ÷ 1.44 ⌉ = ⌈ 76.39 ⌉ = 77 boxes.

Example 3: 15 × 20 ft US kitchen (≈ 4.57 × 6.10 m), 12 × 12 in mosaic tile, 10% waste, 10 tiles/box. Gross area = 15 × 20 = 300 ft² = 300 × 0.09290304 = 27.87 m². Effective area = 27.87 × 1.10 = 30.66 m². Tile area = 1 × 1 = 1 ft² = 0.09290304 m². Tiles = � 30.66 ÷ 0.09290304 ⌉ = ⌈ 330.01 ⌉ = 331 tiles. Boxes (tiles-per-box mode) = � 331 ÷ 10 ⌉ = ⌈ 33.1 ⌉ = 34 boxes. In area-per-box mode with the box covering 10 ft² (10 × 1 ft²), boxes = ⌈ 30.66 ÷ 0.9290304 ⌉ = ⌈ 33.00 ⌉ = 33 boxes, a 1-box rounding gap because the unit conversion introduces a small residual. Both are acceptable; pick the mode that matches how the box is labelled.

Example 4: multi-room job, 5 × 5 m bathroom + 3 × 4 m en-suite, 60 × 60 cm porcelain, 10% waste, 1.44 m²/box. Gross area = 25 + 12 = 37 m². Effective area = 37 × 1.10 = 40.7 m². Tiles = ⌈ 40.7 ÷ 0.36 ⌉ = � 113.06 ⌉ = 114 tiles. Boxes = ⌈ 40.7 ÷ 1.44 ⌉ = ⌈ 28.26 ⌉ = 29 boxes.

Example 5: cost check, 5 × 5 m room, 60 × 60 cm porcelain, 10% waste, 1.44 m²/box, $35 per box. Effective area = 27.5 m². Boxes = ⌈ 27.5 ÷ 1.44 ⌉ = ⌈ 19.10 � = 20 boxes. Cost = 20 × $35 = $700. Tiles in this order = 20 × 4 = 80 tiles (rounded up from 77 needed, so 3 spares for future repairs).

Example 6: high-waste job, 6 × 4 m herringbone kitchen, 30 × 60 cm plank tile, 20% waste, 1 m²/box. Gross area = 24 m². Effective area = 24 × 1.20 = 28.8 m². Tile area = 0.30 × 0.60 = 0.18 m². Tiles = ⌈ 28.8 ÷ 0.18 ⌉ = ⌈ 160 � = 160 tiles. Boxes = ⌈ 28.8 ÷ 1 � = 29 boxes. The 20% waste allowance absorbs the diagonal and herringbone overhead per TCNA Handbook 2024 guidance, for a true herringbone on a 30 × 60 cm plank, push the slider to 22 to 25%.

Where It Shows Up

• DIY bathroom and kitchen renovations. The most common case: a homeowner measures the floor or wall, picks a tile, and wants to know how many boxes to order. The calculator's presets cover the standard residential room sizes (5 × 5 m small bath, 10 × 10 m open-plan kitchen, 15 × 20 ft US kitchen, etc.) and the standard residential tile sizes (30 × 30 cm, 60 × 60 cm, 30 × 60 cm, 12 × 12 in, 18 × 18 in).
• Professional tiler takeoff sheets. A contractor quotes a job by computing the gross area, applying a waste allowance, dividing by the box coverage, and rounding up. The calculator does the same arithmetic, so the per-room numbers on a takeoff sheet match what the calculator returns within a tile or two.
• Multi-room renovation jobs. A whole-house re-tile, a bathroom-and-en-suite combination, a kitchen-plus-pantry layout, the multi-room mode sums the gross area across all rooms before applying the waste multiplier, so the order quantity is correct even when individual rooms are small.
• Bathroom and shower walls. Wall tiling uses the same math, but the room dimensions become wall dimensions (length × height for a single wall, or perimeter × height for a whole room). The TCNA Handbook 2024 waste allowance for walls is the same 10% grid / 12 to 17% cut-up as for floors.
• Backsplashes and small feature walls. A 4 m² kitchen backsplash with 10 × 10 cm subway tiles is a 400-tile job at 10% waste, the calculator handles it without any change in workflow.
• Outdoor patios and pool surrounds. Outdoor tiling typically needs a slightly higher waste allowance (12 to 15%) because of weather-related breakages, awkward cuts against walls, and the higher cost of returning partial boxes. The waste slider accepts any value from 0 to 50%.
• Trade quotes and customer estimates. A contractor can type a customer's room dimensions and tile choice into the calculator during the on-site visit and produce a same-day quote that the customer can take to a trade supplier. The optional cost-per-box field lets the calculator output the material cost in the customer's currency.

Common Mistakes

• Forgetting to add waste. A bare floor-area calculation undercounts by 10% on a rectangular grid and by 20 to 25% on a herringbone. The TCNA Handbook 2024 default is 10% for a straight grid; never order with 0% waste unless the room is a single rectangle with no cuts.
• Subtracting doors and windows without thinking. Doors and windows reduce the gross floor (or wall) area, but a calculator that takes room length × room width does NOT subtract them automatically. This calculator uses the gross rectangle; if your room has a 1.8 m² door, subtract it from the gross by shrinking the length or width in the inputs.
• Choosing the wrong unit. A 600 × 600 mm tile is 0.36 m²; a 600 × 600 cm tile would be 36 m²; a 60 × 60 cm tile is the same as the 600 × 600 mm tile but with different digits in the input. Use the centimetres toggle and type 60 for the standard porcelain tile.
• Confusing tiles-per-box with area-per-box. A 30 × 30 cm ceramic box from a UK trade supplier covers about 1 m² and contains about 11 tiles; a 60 × 60 cm porcelain box covers about 1.44 m² and contains 4 tiles. Pick the packaging mode that matches the side of the box; the calculator handles both.
• Forgetting to round up. A tile left over is reusable on the next project (or as a future repair spare); a tile short means a delivery delay. The calculator always rounds the tile and box counts UP, if you have 27.5 m² to cover, you get 28 boxes, not 27.
• Buying all tiles from the same dye-lot. Tiles are glazed in batches called dye-lots, and each dye-lot is slightly different in colour and surface finish from the next. If you order the exact number of tiles from one dye-lot and then need to order more from a different dye-lot, the colour mismatch will be visible. Check the dye-lot number on the side of the box and order all boxes from the same dye-lot if you have any choice.
• Ignoring box-coverage rounding. A box that covers 1.44 m² actually covers between 1.42 m² and 1.46 m² in practice (the manufacturer quotes the average coverage, and the tile size varies by ±0.5% from its nominal size due to firing tolerances). The calculator's box-coverage input is exact; reality is ±2%. Buy at least one extra box if the room is critical.
• Forgetting delivery and breakage. Most tile suppliers deliver on a pallet, and the pallet is shrink-wrapped. A few tiles break in transit, typically 1 to 2% of a large order. The TCNA waste allowance covers the installer's mis-cuts, not the delivery breakages; allow an extra 2 to 3% on top for the delivery, especially for stone tiles.

Frequently Asked Questions

Q: How many tiles do I need for a 3 × 3 m bathroom floor? A: For a 3 × 3 m bathroom floor with 60 × 60 cm porcelain tiles in a straight grid, the gross area is 9 m², the effective area at 10% waste is 9.9 m², the tile area is 0.36 m², and the number of tiles is � 9.9 ÷ 0.36 ⌉ = 28 tiles. If you subtract one standard 0.9 × 2 m door (1.8 m²), the net floor area is 7.2 m², the effective area at 10% waste is 7.92 m², and the number of tiles drops to ⌈ 7.92 ÷ 0.36 ⌉ = 22 tiles. In a 1.44 m²/box, that's 8 boxes (or 6 boxes with the door subtracted). The calculator rounds up because you cannot buy a third of a tile.

Q: How many tiles are in a square metre? A: It depends on the tile size. 60 × 60 cm = 2.78 tiles per m² (1 ÷ 0.36). 30 × 30 cm = 11.11 tiles per m² (1 ÷ 0.09). 20 × 20 cm = 25 tiles per m² (1 ÷ 0.04). 30 × 60 cm = 5.56 tiles per m² (1 ÷ 0.18). 60 × 120 cm = 1.39 tiles per m² (1 ÷ 0.72). 12 × 12 in (US) = 1.08 tiles per ft² (1 ÷ 0.929). 18 × 18 in (US) = 0.48 tiles per ft² (1 ÷ 2.79). These are theoretical; the calculator's tile area readout gives the same number with more decimal places.

Q: What waste allowance should I use? A: The TCNA Handbook 2024 standard recommendation is 10% for a straight grid on a rectangular room. Use 12 to 15% for a diagonal layout, 15 to 20% for herringbone, and 12 to 17% for a cut-up room with many corners, alcoves, fixed objects (toilet, basin, kitchen island), or out-of-square walls. A beginner's first room typically needs an extra 5% on top of whatever pattern multiplier applies because of mis-cuts and breakages. The calculator's waste slider accepts any value from 0 to 50%.

Q: How accurate is the box count? A: The math is exact to the precision of the inputs. The tile area is computed from the nominal tile dimensions (60 × 60 cm = 0.36 m² exactly), the box coverage is taken directly from the side of the box, the waste allowance is a fixed multiplier, and the box count is the ceiling of effective area ÷ box coverage. Real-world accuracy is limited by three things: (1) the actual tile size varies by ±0.5% from the nominal due to firing tolerances, (2) the actual room is rarely perfectly rectangular and rarely perfectly square-cornered, and (3) delivery breakages (1 to 2% of a large order) are not covered by the installer's waste allowance. Allow one extra box for delivery breakages on any large order.

Q: Can I use this calculator for walls and shower surrounds? A: Yes. Wall tiling uses the same math, the "room" length becomes the wall length, the "room" width becomes the wall height, and the gross area is the wall area. For a single wall of 4 m × 2.4 m with 30 × 60 cm tiles at 10% waste, the gross wall area is 9.6 m², the effective area is 10.56 m², the tile area is 0.18 m², and the number of tiles is ⌈ 10.56 ÷ 0.18 ⌉ = 59 tiles. For a whole shower surround (typically 3 walls of 1 × 2.4 m each plus one long wall of 2 × 2.4 m), use the multi-room mode and sum the wall areas.

Q: What's the difference between ceramic and porcelain tiles? A: Ceramic tiles are made from a red or white clay, fired at a lower temperature, and have a higher water absorption rate (typically 3 to 7%). Porcelain tiles are made from a denser clay, fired at a higher temperature, and have a lower water absorption rate (typically less than 0.5%). Porcelain is more durable, more stain-resistant, and more expensive. The calculator treats them identically for coverage purposes, the difference is in the per-box coverage, which the box-coverage input captures.

Q: How do I convert between square metres and square feet? A: 1 m² = 10.7639104167 ft² (NIST SP 811, exact by definition since 1959). 1 ft² = 0.09290304 m² (exact). The calculator handles the conversion internally when you switch between metric and imperial input units, the input fields are labelled in your chosen unit, but the internal math is always in m². If you want to convert the result back to your local convention, the readout grid gives you the area in m²; multiply by 10.7639104167 for ft².

Q: What is the difference between "area per box" and "tiles per box"? A: "Area per box" is the convention on the side of most European tile boxes: the box says "covers 1.44 m²" and you divide the effective area by 1.44 to get the box count. "Tiles per box" is the convention on the side of most US mosaic and small-format boxes: the box says "contains 12 tiles" and you divide the tile count by 12 to get the box count. Both modes give the same answer for a given room, tile, and waste allowance, modulo small rounding differences from the unit conversion. Pick the mode that matches how the box is labelled.

Q: Can I add multiple rooms? A: Yes. Tick "Add more rooms" below the cost field, and each additional room takes its own length, width, and unit inputs. The calculator sums the gross area across all rooms before applying the waste multiplier and rounding boxes up. Add as many rooms as you need for a whole-house tile job, a bathroom-and-en-suite combination, or a kitchen-plus-pantry layout. Each additional room has a remove button next to it.

Q: How do I estimate cost? A: Type the per-box cost in your local currency in the optional cost-per-box field. The calculator multiplies the rounded box count by the per-box cost and shows the total in the order summary at the top of the result block. The per-box cost varies significantly by region, material, finish, and supplier, verify the figure against the actual trade quote before ordering. Ceramic boxes typically run $15-$50 per box, porcelain $30-$80, mosaic $20-$60, and natural stone $40-$150, but these ranges are indicative only and your local trade supplier will have the actual figure.

Q: Does the calculator account for grout gap? A: No. The grout gap (typically 2 mm for rectified porcelain, 3 mm for standard ceramic, 4 to 6 mm for rustic or hand-made tile) affects only the visual result, not the tile count, so the calculator does not use the grout value in the math. A 2 mm grout gap on a 60 × 60 cm tile reduces the per-tile coverage by about 1.1% (the grout line takes up 2 mm on each of the four edges, or about 4.7 cm out of 60 cm on each axis), which is well within the 10% waste allowance. If you want to be conservative, bump the waste allowance to 12% for a 2 mm grout gap or 15% for a 4 mm grout gap.

Q: How does the calculator handle rectangular and irregular rooms? A: The calculator handles rectangular rooms directly, type the length and width. For an L-shaped, T-shaped, or irregular room, break the room into a sum of rectangles, type each rectangle as a separate room in the multi-room mode, and the calculator sums the gross area. For an L-shape with an overall rectangle of 6 m × 4 m and a 2 m × 1 m cut-out in one corner, type the overall rectangle (6 × 4) as room 1 and a "negative" rectangle by computing the cut-out separately, or just compute the L-shape area by hand (24 − 2 = 22 m²) and pick a single rectangle that matches.

Q: Can the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size be used for professional or commercial purposes? A: Yes, the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size provides mathematically correct results that are suitable for professional, commercial, and educational use. For high-stakes applications (large commercial contracts, structural tiling), verify results with a domain expert. The formulas used are well-established and validated against reference standards (TCNA Handbook 2024, NIST SP 811).

Q: How often are the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size formulas updated? A: The formulas are based on established industry and international standards and rarely require updates. The TCNA Handbook 2024 waste allowance guidance is the current authoritative source; NIST SP 811 conversion factors (1 in = 0.0254 m, 1 ft = 0.3048 m) are exact by definition since the 1959 international yard and pound agreement. When standards change (e.g. new tile formats become common, packaging conventions evolve), this calculator is updated to reflect the current authoritative source. For the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size, For the Tile Calculator, Tiles, Boxes & Cost from Room + Tile Size, Each calculator's references section lists the specific sources used.

References

• Tile Council of North America (TCNA), TCNA Handbook 2024 (Tile Installation Methods and Standards). The standard reference for ceramic and porcelain tile installation, including the recommended 10% cutting-waste allowance for a straight grid on a rectangular room, 12 to 15% for diagonal layouts, 15 to 20% for herringbone, and 12 to 17% for cut-up rooms with many corners.
• NIST Special Publication 811 (2008 ed., "Guide for the Use of the SI Units"), Appendix B.6. The canonical US reference for unit conversions; documents the exact factors 1 in = 0.0254 m and 1 ft = 0.3048 m, both exact by definition since the 1959 international yard and pound agreement.
• Bureau International des Poids et Mesures (BIPM), SI Brochure (9th ed., 2019). The international definition of the metre, the centimetre (SI prefix), and the official conversion factors between metric and imperial length units.
• International yard and pound agreement, 1 July 1959. Signed by the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. Fixed the inch at exactly 0.0254 m and the foot at exactly 0.3048 m, resolving small (~0.0002%) historical differences between US and UK measures.
• British Ceramic Confederation (BCT), Trade guidance on ordering ceramic and porcelain tiles, including the standard 10% cutting-waste rule and pattern multipliers for brick-bond, diagonal, and herringbone layouts.
• ASTM C1067, Standard Practice for Conducting a Wear Test for Tile Installation, covering expected breakage, dye-lot variation, and installation tolerance.

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