How it’s worked out
- Area = the sum of width × height for each wall, minus anything not tiled.
- Tiles = area × (1 + wastage) ÷ one tile’s area. Walls have more cuts than floors around outlets, windows and edges, so don’t skimp on the 10%.
- Adhesive: about 3.5 kg/m² with a 6 mm notch (tiles up to ~300 mm) or 5.5 kg/m² with a 10 mm notch (larger tiles).
- Grout = (L + W) ÷ (L × W) × joint × depth × 1.6 kg per m², plus 10%.
Tiling a floor too? Use the bathroom floor calculator. Tiling is DIY-legal everywhere, but moving taps or power points behind the tiles is licensed work, and shower walls must be waterproofed first (who can do that).
Questions
How many wall tiles do I need?
Measure each wall (width × height of the tiled area), add them up, subtract windows and doors, add 10% for cuts (15% for patterned layouts or lots of cuts), then divide by the area of one tile.
How much tile adhesive for a splashback?
Wall tiles usually go on with a 6 mm notched trowel for small tiles and 10 mm for larger ones, using roughly 3.5–5.5 kg per m². A typical 3 × 0.6 m splashback (1.8 m²) needs well under one 20 kg bag, and pre-mixed tubs are handy for small jobs.
Do I need to waterproof before tiling walls?
In a shower, the walls must be waterproofed to at least 1800 mm under the NCC before tiling. Kitchen splashbacks and most other walls don’t need a membrane.
What size tile trim do I need?
Match the trim to the tile thickness, and measure every exposed tile edge and external corner. The calculator adds 10% to the trim length for cuts and joins.
Estimates only. Check the product label and your measurements before you buy. More free tools: see them all.