Tile Calculator
Calculate the number of tiles and boxes for a floor or wall, including grout gap and waste allowance.
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How to Calculate
Divide the area in square feet by the area of one tile including its grout joint.
Add 10% waste for straight layouts and 15–20% for diagonal or herringbone patterns.
Buy all boxes from the same lot so color and size match.
See our methodology for how every calculator on this site is built.
Worked Example: A Bathroom Floor in 12 × 24 Tile
The floor is 8 ft by 5 ft. Tile is 12 × 24 inches with a 1/8 inch grout joint, 8 tiles to a box, and we'll allow 10% for waste.
- Floor area: 8 × 5 = 40 ft²
- Tile with joint: (12.125 × 24.125) ÷ 144 = 2.03 ft²
- Tiles before waste: 40 ÷ 2.03 = 19.7
- With 10% waste: 19.7 × 1.10 = 21.7, round up to 22 tiles
- Boxes: 22 ÷ 8 = 2.75, so 3 boxes (24 tiles)
Two spare tiles is right where you want to be. In a small bathroom, cuts around the toilet, tub and door jamb eat more than you'd think. If you're running a 1/3 offset pattern with large-format tile, 15% is safer.
Common Tile Sizes
Box counts vary by manufacturer and thickness. These are typical, so check the label for the exact square footage per box.
| Tile size | Area per tile | Tiles per 100 ft² (no waste) | Common box |
|---|---|---|---|
| 3 × 6 in (subway) | 0.125 ft² | 800 | Sold per ft², often 5–12 ft² boxes |
| 6 × 24 in (wood-look plank) | 1 ft² | 100 | 12–16 per box |
| 12 × 12 in | 1 ft² | 100 | 10–15 per box |
| 12 × 24 in | 2 ft² | 50 | 6–8 per box |
| 24 × 24 in | 4 ft² | 25 | 3–4 per box |
The figures above ignore grout joints. With small tile the joints add up: a 3 × 6 subway with 1/16 inch joints covers about 3% more area per tile than its face size.
Mistakes That Cost You Tile
Not planning the layout first
Dry-lay a row in each direction before you mix any thinset. If the layout leaves a 1 inch sliver along a wall, shift the starting line so both sides get cuts of at least half a tile. Slivers break, look bad and waste tile.
Ignoring lippage on long tiles
Tiles 18 inches and longer have a slight bow from the kiln. Laying them in a 50% offset puts the high middle of one tile next to the low end of another. Most manufacturers say to keep the offset at 1/3 or less, and a leveling clip system helps a lot.
Mixing lots
Each box has a lot or caliber number. Tiles from different lots can be a slightly different shade or size. Buy everything at once, check the numbers match, and pull from several boxes as you go so any variation spreads out.
Skipping back-buttering
Large-format tile needs thinset on the back as well as the floor to get full coverage. Hollow spots crack under load.
Other Materials to Plan For
- Thinset: large-format tile needs a big-notch trowel and more mortar per square foot. Plan extra bags.
- Grout: wider joints and smaller tiles use more. Coverage charts are on the bag.
- Backer board or an uncoupling membrane, sized to the same area as the floor.
- Transition strips at doorways, and edge trim for any exposed tile edges on walls.
Rough Cost
Ceramic floor tile commonly runs about $1 to $5 per ft², porcelain about $3 to $10, and natural stone more. Thinset, grout, membrane and trim typically add a few dollars per square foot on top.
Sources
Common questions
Frequently Asked Questions
How much extra tile should I buy?
10% for standard layouts, 15–20% for diagonal or complex patterns, plus a few spares for future repairs.
What grout gap should I use?
1/16–1/8 in for rectified porcelain, 3/16–1/4 in for handmade or uneven tiles.
How many 12×12 tiles in 100 sq ft?
About 100 tiles before waste — 110 with a 10% allowance.
How much thinset do I need?
A 50 lb bag covers roughly 40–60 ft² with a 1/4 × 3/8 in notch trowel, and less with the larger trowels used for big-format tile.
Can I tile over existing tile?
Only if the old tile is solidly bonded, flat and not cracked. Check that the added height still clears doors and appliances.