The formula, wastage percentages, tile adhesive, box quantity, and worked examples for bedrooms, bathrooms, and kitchens.
Ordering the wrong quantity of tiles causes two very different headaches depending on which way it goes. Order too few, and a repeat order weeks later risks arriving from a different production batch — tile dye lots vary slightly between runs, so a "matching" second order can look faintly, but visibly, different once laid next to the first. Order too many, and money sits in stacked boxes that may or may not get used on a future project.
Getting the number right the first time, with a sensible buffer for cutting and breakage, avoids both problems. The math itself is simple — total area divided by the area of one tile — but several details trip most people up: the wastage allowance, converting between the unit a room is measured in (usually feet) and the unit a tile box is labeled in (usually millimeters), and separately estimating adhesive so the job isn't held up mid-way through.
This guide walks through the full calculation, along with room-specific examples for a bedroom, a living room, a bathroom, and a kitchen backsplash — the four situations most people searching for a tile calculator are actually planning for.
Room Area is length × width of the space to be tiled, in square feet. Tile Area is the length × width of a single tile, converted to the same unit. The wastage multiplier accounts for tiles lost to cutting at edges, corners, and around fixtures.
Rather than doing this by hand every time, the Tile Calculator takes room dimensions or a known area, tile size in any unit, and a wastage percentage, and returns the tile count, box quantity, and estimated cost in one step — the same formula below, done instantly.
| Tile size | Typical use | Tiles per sq ft (approx.) |
|---|---|---|
| 300 × 300 mm | Small rooms, bathrooms | 1.0 |
| 300 × 450 mm | Wall tiles, kitchens | 0.75 |
| 600 × 600 mm | Living rooms, floors | 0.25 |
| 800 × 800 mm | Large living areas | 0.14 |
| 600 × 1200 mm | Premium large-format floors | 0.125 |
Larger tiles mean fewer grout lines and a more seamless look, but they also mean each cut piece wastes more material — a factor worth weighing alongside the aesthetic preference, especially for a small or irregularly shaped room.
| Room type | Commonly used size | Why |
|---|---|---|
| Bedroom / living room floor | 600×600mm or 800×800mm | Fewer grout lines across large open areas |
| Bathroom floor | 300×300mm | Easier to cut around drains, fixtures, and slope |
| Bathroom wall | 300×450mm or 300×600mm | Standard wall-tile proportions, easy vertical layout |
| Kitchen backsplash | 100×300mm (subway) or 300×450mm | Fits neatly between counter and cabinet height |
| Balcony / exterior floor | 300×300mm anti-skid | Textured, slip-resistant finish in a manageable size |
Wastage covers tiles lost to cutting at edges, corners, door frames, and the occasional breakage in handling. A simple rectangular room with no obstructions gets away with as little as 5%, since most cuts are clean, usable pieces.
Large-format tiles also deserve a slightly higher buffer in smaller or irregularly shaped rooms, since a single cut can turn one expensive tile into two unusable fragments if neither half fits the remaining space.
The area-based formula is identical for both tile types — what changes is the wastage buffer and, sometimes, the adhesive. Vitrified tiles are fired at a higher temperature and are denser and harder than ceramic, which makes them more water- and stain-resistant but also more prone to chipping at the edge when cut with an ordinary tile cutter rather than a wet saw. A slightly higher wastage allowance (10% instead of the standard 8%) is a sensible default when working with vitrified tiles, especially large-format ones.
Ceramic tiles are softer and generally easier and cheaper to cut, which is part of why 5-8% wastage is often enough for a straightforward ceramic floor. Ceramic is also typically less expensive per box, which matters less for the tile count itself but is worth factoring into the overall budget alongside the Cement Calculator and Sand Calculator if the floor is being laid as part of a larger construction job.
Enter your room size and tile dimensions once — get the tile count, box quantity, and cost estimate instantly.
Open Tile Calculator →Tile quantity is only half the material list — adhesive (or traditional cement mortar) is what actually bonds the tile to the floor or wall, and running short mid-job stalls the work just as effectively as running short on tiles. As a rough guide, a standard 20kg bag of tile adhesive, applied with a 4-6mm notch trowel, covers approximately 40-50 sq ft on a reasonably flat surface.
| Notch trowel size | Typical use | Coverage per 20kg bag |
|---|---|---|
| 4mm | Small tiles (under 300mm) | ~50 sq ft |
| 6mm | Medium tiles (300-600mm) | ~40 sq ft |
| 8-10mm | Large-format tiles (600mm+) | ~30-35 sq ft |
Uneven substrates, or a "buttering" technique used on large-format tiles (applying adhesive to both the floor and the back of the tile), increase adhesive consumption beyond these figures, so it's worth rounding up by a bag when working with big tiles or an older, uneven floor. For the underlying screed or bedding layer beneath the tiles, the Cement Calculator and Concrete Calculator handle that separate material estimate.
Bathrooms are usually the one room where both floor and wall get tiled, and each needs its own calculation. A typical 6×5 ft bathroom with a wall height of 7 ft (tiled fully) works out like this using 300×300mm floor tiles and 300×450mm wall tiles:
Note that bathroom wall area should exclude the door opening (and any window), the same way the Paint Calculator deducts openings for wall paint — the logic is the same whether the wall is being tiled or painted.
A kitchen backsplash is usually a narrow strip rather than a full wall — commonly the 2 ft gap between the countertop and the overhead cabinets, running the length of the counter. For a typical 10 ft counter run with a 2 ft tile height:
Backsplash tiling often skips the box-quantity step entirely since the area is small, but the wastage allowance matters more here proportionally — a 10% miscalculation on 20 sq ft can mean an awkward extra supplier visit for just a handful of tiles.
When a contractor or tile supplier provides a material estimate, it's worth cross-checking against an independent calculation before approving the order. Measure the room yourself — or confirm the dimensions they've used match your own measurement — and run the same area and wastage assumptions through the calculator above.
A close match confirms the estimate is reasonable. A large mismatch, especially if the contractor's wastage percentage is unusually high (20%+ without a clear reason like a diagonal pattern), is worth a direct question before the order is placed — sometimes it's a legitimate reason (an irregular room shape, a premium tile with more breakage in transit), and sometimes it's simply padding.
5% for a simple rectangular room, 10% for rooms with more corners or fixtures, and 12-15% for diagonal or herringbone layouts.
For wall tiling, yes. For floor tiling, door openings are usually small enough to ignore.
Commonly 4-10 tiles per box for floor tiles, depending on tile size and brand — check the box or ask the supplier.
Yes, tile dye lots can vary slightly between production runs, so buying everything — including a few spares — from one batch avoids visible color mismatches.
Split an L-shaped room into two rectangles, calculate each separately, and add the totals.
Wall tiles are thinner and lighter for vertical surfaces; floor tiles are thicker and more impact-resistant for foot traffic.
Grout lines add a small amount of extra area needed, which the wastage percentage absorbs rather than requiring a separate calculation.
Smaller tiles like 300×300mm are common for small bathrooms since they need less cutting around fixtures and corners.
Measure the room yourself, run the same area and wastage numbers through this calculator, and compare — a large mismatch is worth asking about before approving the order.
Yes — enter the tile's exact dimensions in mm, inches, or feet, and consider a slightly higher wastage percentage since large-format tiles waste more per cut.
A 20kg bag of standard tile adhesive covers roughly 40-50 sq ft at a typical 4-6mm notch trowel thickness, though coverage varies by adhesive brand and tile size.
With 600x600mm (2x2 ft) tiles, 100 sq ft needs 25 base tiles, or about 27 tiles with 8% wastage. With 300x300mm tiles, it needs 100 base tiles, or about 108 with wastage.
Both use the same area-based formula. Vitrified tiles are denser and harder to cut cleanly, so a slightly higher wastage allowance (10% instead of 8%) is a safer default.
A 10x12 ft room is 120 sq ft. With 2x2 ft tiles, that's 30 base tiles, or roughly 33 tiles with 8% wastage.
They can use the same wastage logic, but bathrooms typically need a higher percentage (10-12%) on both floor and wall due to fixtures, corners, and drain slopes that create more cuts.