How to Measure for Wall Tiles: Quantities, Waste & Preparation

Accurate measuring is one of the most important parts of a wall tiling project. Ordering too little can stop the job and create the risk of needing a later batch, while ordering far too much wastes money and leaves unnecessary material. The basic calculation is simple, but real bathrooms and kitchens contain windows, doors, sockets, niches, cabinets, boxed pipework and other features that can make the final quantity less obvious. This guide explains how to calculate wall tile quantities properly using real products from the current JJ Building Materials wall tile collection.

Always calculate packs using the coverage shown on the exact live product page. Tile dimensions and pack quantities vary between products, so a pack count calculated for one range should not be carried across to another.

Decide the Exact Tiled Area First

Before using a tape measure, decide where the tiled finish will start and stop. In a bathroom, will the tiles run floor to ceiling, stop at half height or cover only shower and bath areas? In a kitchen, will the splashback be limited to the space between worktops and wall units, or continue around a cooker hood, window and open shelves?

The quantity can change significantly if the design is not fixed. Mark the boundaries on a sketch and measure those finished areas rather than the entire room by default.

Measure in Metres

Working in metres keeps square metre calculations straightforward. Measure the width and height of each wall section, then multiply the two figures. A wall measuring 2.4m wide by 2.2m high has an area of 5.28m². Repeat the calculation for every section that will be tiled.

If your tape measure gives millimetres, divide by 1000 to convert to metres. For example, 1850mm is 1.85m. Keeping all figures in the same unit avoids one of the most common measuring errors.

Break Complex Walls Into Simple Shapes

An awkward wall is easier to calculate when divided into rectangles. Measure the main wall first, then add separate rectangles for returns, boxed sections, nib walls and other tiled faces. Write each area down so it can be checked later.

This method is particularly useful in bathrooms where concealed pipework can create several short faces. Each one may look small, but together they can add a meaningful amount of tile.

When Should You Subtract a Door?

A full-size door that will not be tiled can normally be deducted from the wall area. Measure the width and height of the opening and subtract its square metre area. However, if the reveal around the door will be tiled, add the relevant return faces separately.

Do not become too aggressive with deductions. Subtracting every tiny untiled object can create a misleadingly low total because the tiles surrounding those objects still need to be cut.

How to Measure Around Windows

A large window opening can be deducted from the main wall, but remember the reveals. If the sill, head and two side returns will be tiled, each of those surfaces needs its own measurement. The total area of the reveals can offset a surprising amount of the window deduction.

Window position also affects waste because the tile pattern has to be cut around four sides of the opening. A wall with a window may therefore need more allowance than a plain wall of the same net area.

Should You Subtract Sockets and Small Fittings?

Usually there is little benefit in deducting the area of sockets, switches, pipe penetrations or small fittings. The tile must still cover the surrounding area and be cut around the obstacle. The removed portion is often too small to make a meaningful difference to the total coverage calculation.

In kitchens with many sockets, the bigger issue is not their area but the number of cuts. This may justify a slightly more generous allowance depending on the tile size and layout.

Measuring a Kitchen Splashback

Break the splashback into rectangular sections. Measure from the worktop to the underside of wall units and multiply by the length of each run. Add areas behind cooker hoods or open shelves if they will be tiled. For an L-shaped kitchen, measure each wall separately and add the results.

Narrow-format tiles such as Johnson Tiles Spectrum 400x75mm Glazed Ceramic Wall Tiles or Johnson Tiles Kensington 300x75mm Glazed Ceramic Wall Tiles can involve many socket and edge cuts, so the laying pattern should be decided before the final order quantity.

Measuring a Bathroom

Measure each tiled wall individually rather than assuming opposite walls are identical. Older rooms are not always perfectly square, and boxed services or alcoves can change the dimensions. Add the main wall areas, then add niches, window reveals and any tiled sides of bath panels or boxing if applicable.

If the bathroom combines full-height shower tiling with half-height tiling elsewhere, treat these as separate rectangles. A simple sketch with dimensions beside each face makes the calculation easier to audit.

Check the Exact Pack Coverage

Once you know the net square metres, open the exact product page and find the live pack coverage. Do not calculate solely from nominal tile dimensions because packs contain different quantities. A product such as Johnson Tiles Skyline 600x300mm Glazed Ceramic Wall Tiles will have a different pack arrangement from Johnson Tiles Opal 152x152mm Glazed Ceramic Wall Tile.

Divide the required square metres by the pack coverage, then round up to whole packs. You cannot normally order a fraction of a pack where the product is sold by the pack.

Why You Need a Waste Allowance

Some tile is lost to cutting, breakage and pieces that cannot be reused elsewhere. The amount depends on the room geometry and laying pattern. A simple straight grid on a plain rectangular wall can be efficient, while herringbone, diagonal layouts, niches and many corners create more offcuts.

Rather than applying the same waste percentage to every job automatically, consider the actual layout. If the project is complex, discuss the allowance with the installer before placing the final order.

How Tile Size Affects Waste

Large tiles create large offcuts when a wall dimension does not divide neatly into the module. Small tiles can fit awkward areas more efficiently but may involve more individual cuts. A 600x300mm tile on a broad simple wall can be very efficient, while the same tile around several small niches may produce significant waste.

Compare the tile dimensions with the wall measurements. If the main wall is only slightly wider than one large tile, a centred layout may require two substantial edge cuts. Planning this before ordering helps estimate how much material will actually be usable.

How Herringbone Changes the Calculation

Herringbone creates angled cuts around almost every boundary. It therefore tends to produce more offcuts than straight stack or simple brick bond. Narrow products such as Johnson Tiles South Bank 245x75mm Glazed Ceramic Wall Tiles can be visually effective in herringbone, but the pattern should be dry-planned before finalising quantity.

Horizontal vs Vertical Layouts

Changing the direction of a rectangular tile can alter waste. A 300mm-long tile may divide neatly across a wall horizontally but require many cuts when turned vertically, or vice versa. Products such as Johnson Tiles Chroma 300x100mm Glazed Ceramic Wall Tiles can look very different in each orientation, so choose the direction before calculating packs.

Measure Niches as Five Surfaces

A recessed niche is more than the rectangular back panel. It normally has a back plus top, bottom and two sides. Measure every tiled face. If the niche is using the same tile as the main wall, add all of these areas to the total. If it uses a separate feature tile, keep the measurements separate.

Niches also create additional cuts where the main wall tile meets the opening. This can increase waste even if the additional square metre area is small.

Measure Boxed Pipework and Returns

Boxed pipework often has a front and one or two visible sides. Add every face that will be tiled. Short returns beside a bath, shower or vanity are easy to forget, yet these details can be exactly where spare material is needed for difficult cuts.

Keep Spare Tiles After the Project

Keeping several spare tiles is useful for future maintenance. If plumbing or electrical work damages a tile later, an original spare is far easier to match than a replacement purchased years afterwards. Product ranges and manufacturing batches can change over time.

Store spares securely and label them with the room and product name. This is especially useful when several similar tiles have been used around a property.

Check the Wall Before Ordering Fixing Materials

Quantity planning should include the substrate. Loose plaster, uneven surfaces, damp problems or unsuitable existing finishes may need work before tiling. Large tiles can demand particularly flat backgrounds. If preparation changes the finished wall dimensions or introduces boards, the setting-out plan may also change.

Wet-Area Preparation

In shower areas, the tile itself should not be treated as the complete waterproofing solution. The correct substrate preparation, waterproofing or tanking system, adhesive, grout and sealant details need to work together. Confirm the system before work starts so the correct materials are ordered at the same time as the tiles.

Choose Adhesive and Grout After the Tile

Fixing products should be selected for the actual tile material, format and substrate. Ceramic and porcelain can involve different considerations. Johnson Tiles Melrose 240x69mm Glazed Porcelain Wall Tiles, for example, are porcelain, while Johnson Tiles Prismatics Glazed Ceramic Wall Tiles are ceramic. Check the relevant manufacturer guidance instead of assuming the same fixing product is suitable for every wall tile.

A Worked Example

Imagine two bathroom walls each measuring 2.4m by 2.2m, plus a third wall measuring 1.8m by 2.2m. The first two walls total 10.56m² and the third adds 3.96m², giving 14.52m² before deductions or additions. You would then subtract any large untiled openings, add tiled reveals or niches and apply an appropriate allowance for the chosen layout.

The final pack count is calculated from the live pack coverage of the selected tile. Always round up to whole packs and review the calculation before ordering.

Common Measuring Mistakes

Frequent errors include mixing millimetres and metres, forgetting window reveals, subtracting every small fitting, failing to account for a herringbone layout, rounding down pack quantities and measuring before the final design is agreed. Another mistake is assuming all products in one collection have the same pack coverage.

Measure twice, write everything down and have the installer check complex projects. Good quantity planning reduces delays and makes it more likely that all visible tiles come from the same order.

Wall Tile Measuring FAQs

How do I calculate square metres for wall tiles?

Multiply the width of each tiled section by its height in metres, then add all tiled sections together.

Should I subtract windows and doors?

Large untiled openings can usually be deducted, but add any tiled reveals separately. Small sockets and fittings are generally not worth subtracting.

How much extra tile should I order?

Allow extra for cuts, breakages and the laying pattern. The appropriate amount depends on room complexity, tile size and design, so complex projects should be checked with the installer.

Do I need spare tiles?

Keeping a few spares is sensible for future repairs because ranges, colours and batches can change.

Where can I check pack coverage?

Open the exact tile in the JJ Building Materials wall tiles range and use the live pack information shown for that product.