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.

16 ft × 13 ft kitchen floor, 24-inch porcelain tiles, 1/8-inch grout gap, laid in a straight grid:

1. Floor area: 16 × 13 = 208 sq ft.
2. Each laid tile covers 24.125 in × 24.125 in ≈ 4.04 sq ft including its grout share.
3. 208 ÷ 4.04 ≈ 51.5 → 52 whole tiles to cover the floor.
4. Add 10% for a grid layout: 51.5 × 1.10 ≈ 56.6 → buy 57 tiles (15 boxes at 4 per box).

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

Layout	Allowance	Why
Straight grid	10%	Cuts only at the room perimeter
Offset / brick / diagonal	15%	Every other row starts with a cut
Herringbone / chevron	20%	Diagonal cuts at every edge

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.

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.
• For substrate, movement-joint and wet-area details that go beyond the tile count, the TCNA Handbook for Ceramic, Glass, and Stone Tile Installation is the industry reference in North America.