Tile Calculator
How many tiles do I need? Count tiles by size, grout gap and waste — plus boxes and cost.
How to calculate how many tiles you need
- Measure the area. Length × width for floors; width × height for walls. Split irregular spaces into rectangles and add them up.
- Add waste. 10% for straight layouts, 15% for diagonal or patterned layouts. Waste covers cuts, breakage, and spare tiles for repairs.
- Divide by the area one tile occupies. That is the tile's size plus the grout gap on each side: (width + gap) × (height + gap). Round up — tiles are sold whole.
Formula: tiles = ⌈area × (1 + waste%) ÷ ((tile W + gap) × (tile H + gap))⌉
Common tile sizes
The most popular floor tiles are 12×12 in (300×300 mm), 12×24 in (300×600 mm), and 24×24 in (600×600 mm). Classic 3×6 in (75×150 mm) subway tile remains the default for kitchen and bathroom walls. Larger tiles mean fewer grout lines and faster coverage, but more waste in small or irregular rooms because each cut discards more material.
Grout gap guidance
- 1/16–1/8 in (2–3 mm) — rectified porcelain and ceramic with tight tolerances.
- 1/8–3/16 in (3–5 mm) — standard ceramic floor tile; the most common choice.
- 3/16–1/4 in (5–6 mm) — handmade, natural stone, or irregular tiles.
Frequently asked questions
How much extra tile should I buy?
10% extra for a straight grid, about 15% for diagonal or herringbone layouts and rooms with many cuts. The extra covers breakage, cutting waste, and future repairs from the same dye lot.
Does the grout gap change how many tiles I need?
Slightly — each joint adds to the area a tile occupies, so wider joints mean marginally fewer tiles. This calculator adds the gap to each tile's dimensions, which is why its counts run a little lower than calculators that ignore grout lines.
What is a dye lot and why does it matter?
Tiles are made in batches, and color varies subtly between batches. Buy everything — including the waste allowance — from the same lot number, because a later top-up from a different lot may not match.
Can I use this for wall tile too?
Yes. Enter the wall area (width × height, minus large openings like windows). The waste guidance is the same.