How to Measure a Room for Tiles

Getting accurate room measurements is the single most important step before buying tiles. Measure wrong and you end up with too few tiles mid-project or boxes of expensive leftovers gathering dust in the garage. This guide walks you through measuring rectangular rooms, L-shaped rooms, alcoves, and window recesses — everything you need before plugging numbers into our tile quantity calculator.

What You Need Before You Start

Gather these tools before measuring. Having everything to hand saves time and reduces mistakes.

• A 5-metre retractable tape measure (steel blade, not fabric)
• A notepad and pencil — not your phone, which locks during messy jobs
• A spirit level or laser level for checking walls are plumb
• Masking tape for marking reference points on the floor

A laser distance measurer speeds things up in larger rooms but is not required. For most bathrooms and kitchens, a standard tape measure is perfectly accurate.

Measuring a Rectangular Room

Start with the simplest case: a room with four straight walls and no alcoves.

Measure the length along the longest wall at floor level — not at waist height, because walls are rarely perfectly vertical. Hook the tape on the skirting board at one end and read the measurement where the tape meets the opposite skirting. Write this down immediately.

Now measure the width across the shorter dimension, again at floor level. Take this measurement at two points (near each end of the room) and use the larger figure. If the two readings differ by more than 20 mm, your room is slightly out of square — common in older houses — and the larger figure ensures you order enough tiles.

Your floor area is length multiplied by width. A room measuring 3.2 m × 2.5 m gives 8.0 square metres. Add your waste percentage (10% for a straight layout) and you have 8.8 square metres of tiles to order.

Measuring an L-Shaped Room

L-shaped rooms appear everywhere — kitchens that wrap around a corner, bathrooms with a separate shower alcove, hallways with a turn. The trick is splitting the L into two rectangles.

Stand in the room and identify where the L bends. Place a strip of masking tape across the floor at the inner corner to mark the dividing line between your two rectangles. Now measure each rectangle independently: length and width for the main section, length and width for the extension.

Write both sets of measurements on your sketch with clear labels — "main" and "extension" — so you do not confuse them later. Calculate each area separately and add them together.

For example, a bathroom with a main section of 3 m × 2 m (6 square metres) and a shower extension of 1.5 m × 1.2 m (1.8 square metres) has a total floor area of 7.8 square metres. Our tile calculator handles L-shaped rooms directly — enter both sets of dimensions and it does the addition for you.

Double-check your sketch by measuring the overall outer dimensions of the room. The outer length should equal the sum of the two section lengths (or widths, depending on orientation). If the numbers do not add up, re-measure before ordering.

Handling Alcoves, Chimney Breasts, and Bay Windows

Alcoves (the recesses either side of a chimney breast) add area that is easy to miss. Measure the depth and width of each alcove separately and add these areas to the main room total.

A chimney breast projecting into the room reduces the floor area, but most tilers tile up to the chimney breast rather than around it. Unless the chimney breast is very large (over 0.5 square metres), ignore the reduction — the extra tiles become your built-in waste allowance.

Bay windows are measured as a separate rectangle from the inner wall line to the window sill. Measure the width across the bay opening and the depth from the wall to the furthest point. A bay measuring 1.8 m × 0.6 m adds 1.08 square metres to your total.

Measuring Walls for Wall Tiles

Wall tile measurement follows the same logic but in the vertical plane. Measure each wall individually — do not assume opposite walls are the same size.

For each wall, measure the width along the bottom and the height from floor to the point where tiles will stop. In a bathroom, tiles often run to 2.1 m (just above the shower head) rather than full ceiling height. Record both figures.

Deduct openings from each wall. A standard interior door opening is roughly 0.76 m × 2.04 m (1.55 square metres). A typical window is about 1.2 m × 1.25 m (1.5 square metres). Measure your actual door and window openings rather than relying on these averages — older properties often have non-standard sizes.

If you are tiling both floor and walls, you might find our paint quantity guide useful for the untiled wall sections, since the measurement approach for paint is identical to the wall tile calculation minus the deductions.

Window Recesses and Sill Returns

Window recesses (the inset around the window) are often forgotten. If you plan to tile the reveal around a window, measure three surfaces: the two side returns and the sill or head return.

Each side return is the depth of the wall (typically 100–300 mm in newer builds, up to 400 mm in stone or cavity walls) multiplied by the window height. The sill return is the window width multiplied by the wall depth. Add all three to your wall tile total.

A window recess on a 250 mm deep wall around a 1.2 m × 1.25 m window adds: two sides (0.25 × 1.25 × 2 = 0.63 square metres) plus a sill (1.2 × 0.25 = 0.30 square metres) — roughly 0.93 square metres total. That is easy to miss, and it is enough to need several extra tiles.

Recording Your Measurements

Draw a rough floor plan on your notepad before measuring. It does not need to be to scale — just a shape that shows the room layout with labelled dimensions. Mark north or the door position so you can orient yourself later.

Write measurements in metres with one decimal place (3.2 m, not "three metres and a bit"). Note the date on your sketch. If you are measuring multiple rooms, put each room on a separate page with a clear heading.

Photograph your sketches with your phone as a backup. Pencil on paper can smudge, especially in a damp bathroom. If you are measuring several rooms across the house, number each sketch and keep a running list of rooms completed versus rooms still to measure. This avoids the frustration of discovering a missed room after you have already packed away the tape measure and ordered materials.

Common Measurement Mistakes

Even experienced DIYers make these errors. Check each one before ordering tiles.

• Measuring at waist height instead of floor level — walls lean inward or outward, and the floor dimension is what matters for floor tiles
• Forgetting the alcoves either side of a chimney breast
• Assuming opposite walls are the same length — they rarely are in UK houses
• Using a fabric tape measure that stretches under tension
• Mixing up metres and millimetres on the same sketch

The most expensive mistake is undermeasuring. Running out of tiles mid-project means a second delivery (and possibly a different batch shade). Overmeasuring by 10% costs a few extra pounds but saves a potential delay of days.

From Measurements to Materials

Once you have your measurements, you can calculate material quantities. For floor tiles, you need the tile count, grout, and adhesive. For wall tiles, the same applies but with different adhesive rates. Our tile calculator handles rectangular, L-shaped, and U-shaped rooms and outputs all three material quantities at once.

If you plan to wallpaper sections of the room rather than tile them, measure those walls separately and exclude them from the tile area. Similarly, if you are installing laminate flooring in an adjacent room, take those measurements at the same time to avoid a second measuring session.

For outdoor projects like a patio or garden path, the same measurement principles apply — divide complex shapes into rectangles, measure at ground level, and add waste.