tile calculator
Tile Calculator
Floor or wall, straight or diagonal — get tiles, boxes, thinset and grout.
Reading the result
The tile count assumes you cut from full tiles at the perimeter and cannot reuse most offcuts. Boxes matter more than tiles: tile is sold by the box, dye lots vary between batches, and a box bought later almost never matches. Buy the extra box now.
The formula
How this calculator works
Area = length × width
Effective tile = (tile side + grout joint)²
Tiles per sq ft = 144 ÷ effective tile area in sq in
Tiles = ceil( Area × tiles per sq ft × (1 + waste + diagonal) )
Boxes = ceil( Tiles ÷ tiles per box )
Thinset bags = ceil( Area ÷ coverage per bag ) (50 sq ft floor / 65 wall; 35 / 45 over 12 in tile)
Grout = Area × joint ratio × 0.5 lbGrout joints are part of the module, not a rounding error. A 12 in tile with a 1/8 in joint occupies 12.125 in of floor, so a hundred square feet takes 98 tiles rather than 100. It is a small correction on small tile and a large one on mosaic, where a 1/4 in joint between 2 in tiles changes the count by more than 20 percent.
The diagonal option adds five percentage points on top of your waste factor because a 45 degree layout produces two cut edges at every wall instead of one, and the triangular offcuts are almost never reusable. Herringbone and chevron behave the same way; treat them as diagonal. Running bond and straight stack are the cheap layouts.
Thinset coverage depends on the notch trowel, which in turn depends on tile size. A 1/4 in square notch covers about 50 sq ft per 50 lb bag on floors for tile up to 12 in on a side; on walls, where the bed runs thinner, that rises to about 65. Cross the 12 in mark in either dimension and TCNA guidance calls for a 1/2 in notch, which drops coverage to about 35 sq ft on floors and 45 on walls — the calculator switches to those numbers automatically once you pick a large-format size like 12 × 24 or 18 × 18.
Worked example
Worked example: a 12 × 10 ft floor in 12 × 24 in tile
- Area12 × 10 = 120 sq ft
- Effective tile(12.125 × 24.125) = 292.5 sq in = 2.03 sq ft
- Raw tile count120 ÷ 2.03 = 59 tiles
- Waste at 10%59 × 1.10 = 65 tiles
- Boxes at 8 per boxceil(65 ÷ 8) = 9 boxes
- Thinsetceil(120 ÷ 35) = 4 bags at 50 lb (large-format floor)
- Grout120 × 0.5 ≈ 60 lb
Nine boxes covers 72 tiles, which leaves seven spares. That is the right amount to hold back for future repairs — enough for a couple of cracked tiles, not enough to feel wasteful.
Reference
Tiles per square foot by size
| Tile size | With 1/8 in joint | With 1/4 in joint |
|---|---|---|
| 3 × 6 in subway | 7.0 | 6.4 |
| 6 × 6 in | 3.87 | 3.56 |
| 12 × 12 in | 0.98 | 0.94 |
| 12 × 24 in | 0.49 | 0.47 |
| 18 × 18 in | 0.44 | 0.42 |
| 24 × 24 in | 0.25 | 0.24 |
Reference
Waste factor by layout
| Layout | Recommended waste | Why |
|---|---|---|
| Straight / grid | 10% | One cut edge per wall |
| Running bond (offset) | 10–12% | Staggered ends need more part tiles |
| Diagonal 45° | 15% | Two cut edges per tile at every wall |
| Herringbone / chevron | 15–20% | Angled cuts, unusable offcuts |
| Large format over 24 in | 15% | A single bad cut costs a whole tile |
Questions
Frequently asked
How many tiles do I need for a 10 × 10 room?
100 sq ft of floor takes about 98 12 × 12 tiles before waste, or 108 with a 10% allowance. In 12 × 24 tile the same floor takes 49 tiles, 54 with waste.
How much extra tile should I buy?
10% for a straight layout, 15% for diagonal or herringbone, and always round up to a whole box. Keep the spares — dye lots shift between production runs and a replacement box a year later will read as a different colour under daylight.
Do I include grout joints in the calculation?
Yes, and this calculator does it automatically. The joint adds to the module size, so wider joints mean fewer tiles. It makes a negligible difference on large-format tile and a substantial one on mosaic.
How much thinset do I need?
Roughly one 50 lb bag per 50 sq ft on floors with a 1/4 in square-notch trowel (tile up to 12 in), or per 65 sq ft on walls. Cross 12 in in either dimension and the required 1/2 in notch drops that to about 35 sq ft on floors and 45 on walls — figure on close to 40% more mortar for large-format tile.
How much grout do I need?
About half a pound per square foot for 12 in tile at a 1/8 in joint. Smaller tile and wider joints raise it sharply — mosaic with 1/4 in joints can approach two pounds per square foot.
What size trowel should I use?
A 1/4 × 1/4 in square notch for tile up to 12 in, a 1/4 × 3/8 in for 12 to 16 in, and a 1/2 × 1/2 in for large format. The rule that matters is coverage: lift a set tile and you want at least 80% of the back contacted, 95% in wet areas.
Can I tile over existing tile?
Sometimes, if the existing tile is well bonded, flat and not over a failing substrate, and if the added height does not create a problem at doors and transitions. Scarify or prime the glaze first. When in doubt, the removal is cheaper than the failure.
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Results are estimates. Actual quantities vary with installation method, site conditions and material waste. Confirm quantities with your supplier or a licensed contractor before making a significant purchase.