How to Measure for Wall and Floor Tiles

Getting Your Tile Quantities Right

Nothing stalls a tiling job like running out of tiles on a Saturday afternoon when the merchant's shut. Order too few and you'll be hunting for matching batch numbers. Order too many and you've wasted money on boxes you can't return once opened. Here's how to measure properly and get your quantities spot on.

Step 1: Measure Your Area

Floor Tiles

For a rectangular room, it's simple:

Area (m²) = Length (m) × Width (m)

A 3m × 2.5m bathroom floor = 7.5 m²

For L-shaped rooms or irregular layouts, break the floor into rectangles, calculate each one, and add them together.

Wall Tiles

Measure each wall you're tiling separately:

Wall area (m²) = Width (m) × Height (m)

Then subtract any areas you're not tiling — windows, doors, shower niches. But be conservative with your deductions. If a window is small (under 0.5 m²), don't bother subtracting it — you'll need tiles to cut around it anyway, and the offcuts often can't be reused.

Example: Standard Bathroom

| Surface | Dimensions | Area (m²) | |---|---|---| | Floor | 2.5m × 2.0m | 5.0 | | Wall 1 (long, with window) | 2.5m × 2.4m, minus 0.6 m² window | 5.4 | | Wall 2 (short) | 2.0m × 2.4m | 4.8 | | Wall 3 (long, with door) | 2.5m × 2.4m, minus 1.6 m² door | 4.4 | | Wall 4 (short, shower wall) | 2.0m × 2.4m | 4.8 | | Total | | 24.4 |

Pop your measurements into the Tile Calculator and it'll work out quantities, wastage, adhesive, and grout for you.

Step 2: Add Wastage

This is where most people go wrong. You will have waste — from cuts that don't produce usable offcuts, breakages, and pattern matching. The percentage depends on your layout:

| Layout Pattern | Wastage Allowance | |---|---| | Straight (grid) | 5–7% | | Brick bond (offset) | 7–10% | | Diagonal (45°) | 10–12% | | Herringbone | 12–15% | | Chevron | 15%+ | | Large format tiles in small rooms | 10–15% |

Why Herringbone and Diagonal Need More

When you lay tiles at an angle, every tile that meets a wall needs cutting at an angle. The offcuts are triangular and often too small to use elsewhere. A straight layout produces rectangular offcuts that can frequently be used on the opposite side of the room.

Large Format Tiles

Big tiles (600×600mm and above) in small rooms create more waste because you're cutting more tiles proportionally. A 600×600mm tile in a 2m-wide room means cutting every third tile — and the offcut is often too narrow to use.

Rule of thumb: For most domestic jobs with a straight layout, add 10% and you'll be safe. It's always better to have a few spare tiles tucked away for future repairs.

Step 3: Calculate the Number of Tiles

Once you've got your total area (including wastage), divide by the area of a single tile:

Number of tiles = Total area (m²) ÷ Area of one tile (m²)

Common Tile Sizes

| Tile Size | Area per Tile (m²) | Tiles per m² | |---|---|---| | 100 × 100mm | 0.01 | 100 | | 150 × 150mm | 0.0225 | 44.4 | | 200 × 200mm | 0.04 | 25 | | 200 × 300mm | 0.06 | 16.7 | | 250 × 400mm | 0.10 | 10 | | 300 × 300mm | 0.09 | 11.1 | | 300 × 600mm | 0.18 | 5.6 | | 450 × 450mm | 0.2025 | 4.9 | | 600 × 600mm | 0.36 | 2.8 | | 600 × 1200mm | 0.72 | 1.4 | | 800 × 800mm | 0.64 | 1.6 |

Always round up to the nearest whole tile and then to the nearest full box. Tiles are sold in boxes, and you can't buy individual tiles from most merchants.

Step 4: Work Out Your Adhesive

Adhesive coverage depends on the trowel notch size, which depends on the tile size:

| Tile Size | Trowel Notch | Coverage per 20kg Bag | |---|---|---| | Up to 200 × 200mm | 6mm | 5–6 m² | | 200 × 300mm to 300 × 300mm | 10mm | 3–4 m² | | 300 × 600mm to 600 × 600mm | 12mm | 2–3 m² | | Over 600 × 600mm | 12mm + back-buttering | 1.5–2 m² |

For our 24.4 m² bathroom example with 300 × 600mm tiles:

24.4 ÷ 2.5 (average coverage) = 10 bags of 20kg adhesive

Use a flexible adhesive (S1 rated, conforming to BS EN 12004) for floors, heated floors, and anywhere with movement. Standard adhesive is fine for stable wall surfaces.

Rapid-Set vs Standard

• Standard set — 24-hour drying time, more working time, cheaper. Good for most jobs.
• Rapid set — walkable in 3–4 hours, ideal for kitchens and bathrooms where you need to get back in quickly. Costs about 30% more.

Step 5: Work Out Your Grout

Grout usage depends on tile size, grout joint width, and tile thickness. As a rough guide:

| Tile Size | Grout per m² (approx.) | |---|---| | Small mosaic (up to 100mm) | 1.0–1.5 kg | | 200 × 200mm (3mm joint) | 0.4–0.6 kg | | 300 × 300mm (3mm joint) | 0.3–0.5 kg | | 300 × 600mm (3mm joint) | 0.25–0.4 kg | | 600 × 600mm (3mm joint) | 0.2–0.3 kg |

A standard 5kg bag of grout covers roughly 10–15 m² for medium-format tiles. Buy an extra bag — running out mid-grout means a visible colour difference where you stop and start.

For wet areas, use an epoxy grout or at least a flexible, water-resistant grout. The Tile Association provides comprehensive guidance on tiling in wet rooms. Standard sanded grout will stain and deteriorate in showers.

Tips for Ordering

• Check batch numbers. Tiles from different batches can have slight colour variations. Order everything in one go from the same batch.
• Keep spares. Hold back 3–4 tiles for future repairs. Store them flat somewhere dry.
• Check return policies. Most merchants accept unopened boxes back within 30 days. Don't open boxes until you need them.
• Order early. Some tiles have 4–6 week lead times, especially anything imported or from a specific range.
• Inspect on delivery. Check for chips, cracks, and colour consistency before the driver leaves.

Cutting Around Obstacles

Pipes, toilet flanges, window reveals, and sockets all need cuts. Tips:

• Straight cuts — score and snap cutter for wall tiles, wet cutter for floor tiles and porcelain
• Holes for pipes — diamond hole cutters (about £5–£15 each). Measure twice.
• L-shaped cuts — wet cutter or angle grinder with a diamond blade
• Curves — tile nippers for small adjustments, wet cutter for controlled curves

Budget for a diamond blade wet cutter hire (about £30–£40 per day) if you're doing a full room in porcelain. Porcelain is much harder than ceramic and will destroy a standard score-and-snap cutter.

If you're tiling an external patio area rather than an interior space, the Patio Calculator can help with quantities for outdoor paving and slabs.

Quick Summary

1. Measure each surface separately — length × width for floors, width × height for walls
2. Subtract large openings (doors, big windows) but not small ones
3. Add wastage: 5–7% straight, 10–12% diagonal, 12–15% herringbone
4. Divide total area by tile area to get the number of tiles, then round up to full boxes
5. Budget 2–3 m² coverage per 20kg bag of adhesive for medium/large tiles
6. Use the Tile Calculator to get all your quantities in one go