Bathroom Tile Calculator

How to Calculate Tiles for a Bathroom

Bathroom tiling is one of the most impactful renovations you can make, but it requires careful planning. Bathrooms have unique requirements — waterproofing, slip resistance, and moisture-resistant grout — that set them apart from tiling other rooms.

Bathroom Tile Calculation: Floor vs Walls

Floor tiles: Length × Width of the floor area, divided by the area of a single tile, plus waste.

Wall tiles: Calculate the area of each wall separately (height × length), subtract any windows, then divide by single tile area plus waste.

For a bathroom measuring 2.5m × 3m with 2.5m ceiling height:

Choosing Bathroom Tiles by Area

Different bathroom zones have different requirements:

Waterproofing: The Critical Step

Waterproofing is non-negotiable in bathrooms. Water that gets behind tiles causes mould, structural rot, and costly damage. Here's what you need:

• Liquid membrane — Apply 2 coats with a roller over the entire wet area. Coverage is approximately 1-1.5 L per m² for two coats.
• Reinforcing tape — Use in corners and at wall-floor junctions where movement and cracking are most likely.
• Drying time — Allow 24 hours for the membrane to fully cure before tiling over it.
• Coverage area — At minimum, waterproof the shower zone. Best practice is to waterproof the entire bathroom floor and all walls to at least 1.8m height.

Materials List for Bathroom Tiling

Floor Tiles vs Wall Tiles: Key Differences

Not all tiles are interchangeable between floors and walls:

• Floor tiles must have a slip rating (R9 minimum, R10-R11 preferred for wet areas). They're thicker (8-10mm) and made from denser porcelain.
• Wall tiles can be thinner ceramic (6-8mm) and don't need a slip rating. They're lighter, which prevents them pulling away from the wall under their own weight.
• Floor tiles can go on walls (if the wall structure supports the weight), but wall tiles should never go on floors.

Grout for Bathrooms

Standard grout absorbs moisture and can grow mould. For bathrooms, always use:

• Epoxy grout — Completely waterproof and mould-resistant. More expensive (€8-15/kg) but lasts the life of the tiles.
• Anti-mould cementitious grout — A budget alternative (€3-5/kg) with fungicide additives. Effective but may need resealing every few years.
• Silicone sealant — Use in corners, edges, and where tiles meet the bathtub or shower tray. Grout cracks in these movement zones; silicone flexes.

Common Bathroom Tiling Mistakes

• Tiling before waterproofing — The most costly mistake. Water finds every gap and causes hidden damage.
• Using wall tiles on the floor — They'll crack under foot traffic and lack slip resistance.
• Grout in movement joints — Where walls meet floors, use silicone sealant instead of grout.
• Not planning tile layout — Dry-lay tiles first to avoid thin slivers at edges. Centre your layout so cuts are even on both sides.

When to Hire a Professional Tiler

Bathroom tiling is one renovation where professional skill truly matters. Waterproofing failures are invisible until water damage appears months later. Hire a professional if you're tiling a shower, working with large-format tiles (60cm+), or if you're not confident in your waterproofing technique.