Tile Calculator

How this calculator works

The calculator divides your floor (or wall) area by the footprint of a single laid tile - the tile face plus one grout joint on each side - then adds your wastage allowance and rounds up to whole tiles:

tiles = ceil( (room length × room width) ÷ ((tile width + grout gap) × (tile height + grout gap)) × wastage )

Including the grout joint matters: with small tiles and a wide gap, ignoring it overestimates the count and you buy boxes you don’t need. All math runs in exact metric units internally, so switching between feet and metres never changes the result.

Worked example

This example follows the unit system you pick in the calculator above.

5 m × 4 m floor, 600 mm tiles, 3 mm grout gap, laid in a straight grid:

1. Floor area: 5 × 4 = 20 m².
2. Each laid tile covers 0.603 m × 0.603 m ≈ 0.364 m² including its grout share.
3. 20 ÷ 0.364 ≈ 55 → 56 whole tiles to cover the floor.
4. Add 10% for a grid layout: 55 × 1.10 ≈ 60.5 → buy 61 tiles.

Those extra tiles aren’t optional padding - they cover the cut tiles at the walls, the one or two that crack during cutting, and a spare for repairs years later.

Choosing the right wastage allowance

Small rooms and rooms with many doorways, alcoves or fixtures sit at the high end of each range, because the perimeter is large relative to the area. If your tile is a natural stone with batch variation, round up rather than down - a later batch may not match.

If your job doesn’t fit one of these presets, choose Custom %… in the wastage menu and type your own figure - useful when your tiler has quoted a specific allowance or you’re matching an existing batch.

Tiling floors, walls, showers and backsplashes

The same count works for any tiled surface - measure the area, divide by the tile footprint, add wastage - but each job has its own measuring notes:

• Floor tiles - measure the floor at skirting level and let the tiling run under the threshold of each doorway.
• Wall tiles - multiply each wall’s width by its tiled height. Subtract only large openings (over about 1 m²); small ones are absorbed by the wastage allowance.
• Shower and bathroom walls - tile each wall of the enclosure separately and add them. Small mosaics and feature strips push wastage toward 15–20%.
• Backsplash - measure the run length by the height from worktop to wall units. Backsplashes are mostly cut edges, so round up.

Run the calculator once per surface and add the results, or total the areas first - either way, pick the wastage allowance that matches each layout.

How much does it cost to tile?

The tile count above is what sets the price, so this calculator estimates cost from your numbers rather than a national average that drifts out of date. In the Cost estimate section, pick how you are pricing the job:

• Buy the materials (DIY) - enter your tile price per square metre or foot (the way tile is listed online), and the calculator prices the area of tile you actually take home. Add the adhesive and grout by their bag coverage and price - it divides your tiled area by the coverage on the bag and rounds up to whole bags - and a flat count of spacer packs. Each line is itemised and totalled, so you can see exactly where the money goes.
• Installed price - enter a single tiler’s rate per square metre (or foot). A fitted quote bundles the tiles, adhesive, grout and labour into that one rate, so the cost is simply your tiled area × the rate.

tile cost    = area of tiles bought × price per m²/sq ft
adhesive     = ceil(tiled area ÷ coverage per bag) × price per bag
grout        = ceil(tiled area ÷ coverage per bag) × price per bag
installed    = tiled area × installed rate per m²/sq ft

This calculator assumes the wall or floor is already prepared for tiling - so backer board, render, waterproofing, primer and tile trim aren’t included, because they vary far too much by job to estimate sensibly. Leave any price blank to skip it; a partial list still totals. Cost figures are indicative - set each price to a real quote for your area.

Measuring tips

• Measure at floor level along the skirting, not across furniture.
• For walls, multiply width × height per wall and subtract windows and doors only if they’re larger than about a square metre - small openings are usually absorbed by the wastage allowance.
• For L-shaped or irregular rooms, split the space into rectangles and run the calculator once per rectangle.
• Buy all your tiles at once and check the batch/shade number on every box matches.

Tile sizes and standards where you are

In New Zealand, floor and wall tiles are usually sized in millimetres, with 300 × 300 mm and 600 × 600 mm among the common sizes. Enter the tile size you are actually buying in the calculator above so the count matches the boxes on the shelf.

For the recognised installation detail - substrate preparation, adhesive coverage, movement joints and finished tolerances - see the TANZ Best Practice Guide for tiling and wet-area construction.