How the tile calculation works
For a rectangular surface, the calculator multiplies length by width to find gross area. If you already measured several sections, choose known surface area and enter their combined total. An optional excluded area is then subtracted to produce the net area that will actually receive tile. Work in one measurement system at a time: metres and square metres in metric mode, or feet and square feet in imperial mode.
One tile's coverage is width multiplied by length after converting millimetres to metres or inches to feet. Net area divided by tile area, rounded up, gives the theoretical minimum number of whole tiles. The chosen cut and breakage percentage is applied to net area before dividing again. Because retailers sell complete boxes, the allowance-adjusted tile count is divided by tiles per box and rounded up. The result keeps these three forms—minimum tiles, allowance-adjusted tiles and purchasable boxes—separate so box rounding is visible.
Measure floors, walls and irregular spaces
Measure the finished surface rather than relying on a room's advertised floor size. A simple floor needs its maximum length and width. A wall needs the tiled width and height. Divide an L-shaped room, alcove or stepped wall into rectangles, calculate each area, and add the sections. Use the known-area option for that combined figure. Measure each separate wall when heights differ.
The excluded-area field is useful for a large permanent section that definitely receives no tile. Small openings, fixtures and boundaries do not always reduce the purchase quantity by their full geometric area because full tiles are still cut around edges and offcuts may be unusable. When unsure, leave small exclusions in the area and let the waste allowance cover normal cutting. A detailed tile layout is more reliable than aggressive subtraction.
Choose a realistic cut and breakage allowance
No single waste percentage is correct for every project. Straight layouts in a square room can produce fewer offcuts than diagonal, herringbone, staggered or heavily patterned layouts. Many corners, narrow borders, fragile products, mixed shades and an inexperienced installer can increase losses. Large-format tiles may also create substantial unusable pieces even when the number of cuts is small.
The default 10% is an editable starting example, not a recommendation or industry ceiling. Base the entry on the actual tile, layout drawing and installer guidance. For expensive or special-order products, compare the cost of a larger allowance with the risk that matching stock will be unavailable later. The calculator shows the effect transparently; it cannot inspect a plan or predict breakage.
Use the box label, not a generic assumption
Tile dimensions and tiles per box vary by product, market and production batch. Copy both values from the exact listing or carton you intend to purchase. Some retailers emphasize square-metre or square-foot coverage per box rather than tile count. You can verify that claim by multiplying physical area per tile by tiles per box, allowing for normal rounding in the published specification.
Enter the price of one complete box. If a retailer quotes a price per square metre but only sells full boxes, use the checkout price for one box to avoid understating cash cost. The calculator multiplies boxes to buy by that price and does not assume taxes, delivery charges or discounts. It contains no live retailer pricing, so changing market prices cannot silently affect the result.
Why grout joints are not subtracted
A visible grout joint occupies a small part of the finished surface, but subtracting every joint from material quantity can create false precision. Retail box coverage is commonly presented from the physical tile dimensions, and a grout line does not turn a boundary offcut into a new whole tile. Layout, edge cuts and breakage usually matter more than the tiny theoretical reduction from joints. This tool therefore uses physical tile area and leaves grout width out of the purchase formula.
Grout quantity is a separate calculation involving joint width, joint depth, tile thickness and product coverage. Adhesive or mortar also depends on substrate, trowel, bed thickness and product instructions. Neither is inferred from tile area here.
Full boxes, reserve stock and production lots
The minimum-box result already rounds the allowance-adjusted count up to a complete box. That rounding can leave more tiles than the entered percentage alone. “Tiles beyond minimum” shows the total difference between purchased tiles and the theoretical no-waste minimum, including allowance, box rounding and an optional reserve box.
The reserve option deliberately adds one unopened full box. It can be useful for future repairs, concealed plumbing access or maintaining the same shade and calibre. It also raises immediate cost and may be unnecessary when matching stock is dependable or unopened returns are allowed. Check the retailer's return window before ordering and compare batch, dye-lot, shade and calibre identifiers when collecting multiple boxes.
Understand each result before buying
| Result | What it means |
|---|---|
| Net area to tile | Gross measured area minus only the excluded area you entered. |
| Minimum tiles | The mathematical count of whole tiles needed with no allowance. |
| Tiles including allowance | Net area increased by your chosen percentage, divided by one tile's area and rounded up. |
| Minimum full boxes | The allowance-adjusted tile count rounded up to complete packages. |
| Purchased coverage | All tiles in boxes to buy multiplied by one tile's physical area. |
| Estimated tile cost | Boxes to buy multiplied by entered box price, excluding every unentered charge. |
Product choice and installation safety
A quantity result does not establish that a tile is appropriate for the surface. Confirm indoor or outdoor rating, floor or wall suitability, wet-area requirements, slip resistance, frost resistance, substrate preparation and compatible installation products with the manufacturer and applicable local rules. Heavy wall tile, waterproofing, heated floors, movement joints, stairs and structurally uncertain surfaces can require professional assessment.
Wear suitable protective equipment and control silica dust when cutting materials that may contain crystalline silica. Follow the tile and tool manufacturer's instructions and local occupational or building requirements. This calculator does not provide structural, waterproofing or workplace-safety approval.
Current calculation references
- Bunnings Australia tile quantity guide — explains measuring area and converting required coverage into boxes.
- Bunnings New Zealand tile quantity guide — provides the same practical box-based planning approach for New Zealand shoppers.
- B&Q tiling calculator — calculates from surface length and width and distinguishes wall and floor projects.
- Wickes tiling calculator — notes extra material for breakage and awkward cuts.
- Lowe's tile flooring calculator — presents its output as a project estimate rather than a guaranteed order quantity.
Frequently asked questions
How many boxes of tile do I need?
Calculate the allowance-adjusted tile count, divide it by tiles per box, and round up. For example, 37 tiles sold four per box require 10 boxes, because nine boxes contain only 36 tiles.
Can I enter square feet but tile size in inches?
Yes. Choose imperial mode. Project area is calculated in square feet while tile width and length use inches. The tool converts tile dimensions to square feet before dividing.
Does the calculator work for wall tile?
Yes. Enter wall width and tiled height as the rectangle dimensions, or add multiple wall areas and use known surface area. Subtract only large areas that definitely require no tile.
Does the result include labor and installation materials?
No. The displayed cost covers only full tile boxes at the price entered. Adhesive, grout, underlayment, waterproofing, trims, tools, tax, delivery and labor are outside the estimate.
This calculator is independent and currently contains no affiliate links or paid placements. It does not promise an exact order quantity, savings or installation outcome. Future commercial relationships will be clearly labeled and will not change the calculation method or editorial criteria.