How to Measure for Tiles: Calculating Square Metres, Wastage, and Getting Your Order Right

Getting the tile quantity right is more important than most people realise. Order too few and you wait weeks for a restock that may come from a different batch with a slight colour variation. Order far too many and you waste money. The sweet spot is enough tiles to complete the job with a planned wastage margin, plus a box of spares for future repairs.

This guide walks through how to measure accurately and how to calculate the right order quantity.

Grey herringbone kitchen floor, Orpington. Approximately 45 square metres. A herringbone pattern like this needs 15-20% extra over the measured area because every perimeter tile is cut at an angle, creating more waste than a straight lay. Getting the order quantity right before work starts prevents mid-project delays. Kitchen floor tiling service

Step 1: Measure each surface

Floors

Measure the room’s length and width in metres. Multiply them together.

Example: A bathroom that is 2.4m long and 1.8m wide = 2.4 x 1.8 = 4.32 square metres.

For L-shaped rooms, split the floor into rectangles, calculate each one, and add them together.

For rooms with alcoves or bay windows, measure the main rectangle and add the alcove area separately.

Walls

Measure each wall individually. Height x width for each wall. Add all walls together.

Example: A bathroom with four walls:

• Wall 1 (behind bath): 2.4m high x 1.7m wide = 4.08 sqm
• Wall 2: 2.4m x 1.8m = 4.32 sqm
• Wall 3 (with window): 2.4m x 1.7m = 4.08 sqm, minus window (0.6m x 0.8m = 0.48 sqm) = 3.60 sqm
• Wall 4 (with door): 2.4m x 1.8m = 4.32 sqm, minus door (2.0m x 0.7m = 1.40 sqm) = 2.92 sqm
• Total walls: 4.08 + 4.32 + 3.60 + 2.92 = 14.92 sqm

Half-height tiling

If you are only tiling to half height, measure the tile height (e.g. 1.2m) instead of the full wall height in the calculation.

Shower enclosures

Measure the three walls of the shower enclosure separately if they are being tiled to full height while the rest of the bathroom is half-height.

Step 2: Subtract openings

Subtract the area of windows and doors from the wall total. Do NOT subtract small openings like pipe holes, extractor fans, or electrical sockets. The tile still needs to be cut and fitted around these, so the material is used.

Rule of thumb: Only subtract openings larger than 0.5 square metres.

Step 3: Add wastage

Wastage accounts for cutting errors, breakages, edge cuts, pattern matching, and future spare tiles.

Wastage percentages:

Pattern	Wastage to add
Straight lay (brick bond, stack bond)	10%
Third-offset or random offset	10%
45-degree diagonal	15%
Herringbone	15-20%
Chevron	20%
Victorian geometric / complex patterns	20-25%
Mosaic (sheet format)	10%

Example calculation:

• Floor area: 4.32 sqm
• Wall area: 14.92 sqm
• Total tiled area: 19.24 sqm
• Pattern: straight lay (+10%) = 19.24 x 1.10 = 21.16 sqm
• Round up to next full box quantity

Step 4: Convert to boxes

Tiles are sold in boxes covering a specific area. Check the box coverage (printed on the box or listed online).

Example: If the tile comes in boxes of 1.44 sqm each:

• 21.16 sqm / 1.44 sqm per box = 14.7 boxes
• Round up to 15 boxes

Always round up. Never round down. One extra box is cheap insurance against running short.

Step 5: Order check

Before placing the order, verify:

Batch consistency. Confirm with the supplier that all boxes will come from the same production batch. Different batches can have slight colour variations that are invisible in the box but visible on the wall. This is not a defect. It is normal manufacturing variation. Same batch eliminates the risk.

Delivery timing. Order at least two weeks before the tiler’s start date. UK tile supply chains are inconsistent. Out-of-stock delays of two to four weeks are common. See how to prepare for a tiler.

Spare tiles. Keep at least 4-6 spare tiles (a partial or full box) after the job is complete. Store them flat in a dry place. If a tile cracks from impact in five years, your tiler can replace it with an exact batch match. Without spares, finding an identical tile years later is often impossible.

Common measuring mistakes

Forgetting the niche. A recessed shower niche has five interior surfaces that all need tile. Measure the back, top, bottom, and two sides. It adds surprisingly to the total.

Measuring in centimetres and ordering in metres. Make sure your units are consistent. 240cm = 2.4m. A decimal error doubles or halves your order.

Measuring the floor only. The most common mistake. Walls use significantly more tile than the floor in most bathrooms. Do not forget to measure every wall you intend to tile.

Not accounting for tile drenching. If you are using the same tile on floor and all walls to the ceiling, the total area is much larger than just the floor. Measure everything.

Ordering for the room, not the pattern. A herringbone pattern on the same floor uses the same number of tiles as straight lay plus 15-20% more for the angled perimeter cuts. The pattern does not change the room size but it changes the waste significantly.

When to let the tiler measure

Your measurements are for estimating cost and placing the initial order. The tiler will confirm measurements during the site visit and may adjust for:

• Substrate build-up (levelling compound, backer board adds thickness)
• Layout optimisation (adjusting the starting point to minimise cuts)
• Feature details (niches, shelves, boxed-in pipes) that add tiled surfaces

If the tiler’s measurement differs significantly from yours, ask why. The discrepancy is usually explained by surfaces you did not account for or by substrate preparation that changes the effective wall dimensions.

For a precise measurement and tile order calculation as part of a free site visit, get in touch. See also: tile installation guide | how to prepare for a tiler | tiling cost 2026