Tile is sold by the box, so the goal is to buy just enough boxes plus a few spares from the same production batch (dye lot) for future repairs. Including the grout joint in the size of each tile gives a more accurate count; the waste allowance covers cuts at walls and around obstacles – more for diagonal or patterned layouts and large-format tile.
How to use the Tile Calculator
- Area length
- Area width
- Tile length
- Tile width
- Grout joint
- Layout / waste
- Tiles per box
- Price per box
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the area dimensions (or a total area as length × 1), the tile size and joint width, the waste allowance and how many tiles come in a box. The calculator divides the area by the space taken by one tile and its joint, adds waste and rounds up to whole tiles and boxes.
Tips for an accurate estimate
- Sketch the job and split irregular areas into rectangles, circles and triangles before you measure.
- Add a waste allowance – typically 5–10% for simple layouts and 15–20% for diagonal, curved or heavily cut work.
- Check the coverage or yield printed on the product, because sizes and densities vary between manufacturers.
- Buy all units of a finished material (tile, brick, siding) from the same batch so colours match, and keep a few spares for repairs.
- Confirm local prices – quarry, lumber and steel prices vary widely by region and season.
Common mistakes to avoid
- Ordering exactly the calculated amount with no allowance for breakage, offcuts and settlement.
- Forgetting to subtract doors, windows and other openings – or subtracting small ones that still need cutting around.
- Confusing US short tons (2,000 lb) with metric tonnes (1,000 kg) when comparing quotes.
Inputs explained
| Field | What to enter |
|---|---|
| Area length | Units: ft, m, in, yd, cm |
| Area width | Units: ft, m, in, yd, cm |
| Tile length | Units: in, cm, mm, ft, m, mm |
| Tile width | Units: in, cm, mm, ft, m, mm |
| Grout joint | Units: in, cm, mm, ft, m, mm |
| Layout / waste | Choose one: Straight lay – 10%, Brick / offset – 12%, Diagonal – 15%, Herringbone – 20% … |
| Tiles per box | A number |
| Price per box | Units: /piece |
What each result means
- Area = [Area length]×[Area width]
- Tiles needed = ceil([Area]÷(([Tile length] + [Grout joint])×([Tile width] + [Grout joint]))×(1 + [Layout ÷ waste]÷100))
- Boxes = ceil([Tiles needed]÷[Tiles per box])
- Area covered by those boxes = [Boxes]×[Tiles per box]×[Tile length]×[Tile width]
- Cost = [Boxes]×[Price per box]
Example values
How the main result changes when Area length changes and everything else stays at the example values above:
| Area length (ft) | Tiles needed |
|---|---|
| 6 | 65 |
| 9 | 97 |
| 12 | 130 |
| 15 | 162 |
| 18 | 194 |
| 24 | 259 |
Formula
Tiles = area ÷ ((tile L + joint) × (tile W + joint)) × (1 + waste)Boxes = ceil(tiles ÷ tiles per box)Worked example
Inputs — Area length: 12 ft; Area width: 10 ft; Tile length: 12 in; Tile width: 12 in; Grout joint: 0.125 in; Layout / waste: Straight lay – 10%; Tiles per box: 10; Price per box: $25 /piece.
Results — Area = 120 ft²; Tiles needed = 130; Boxes = 13; Area covered by those boxes = 130 ft²; Cost = $325.00.
Frequently asked questions
How many tiles do I need for 100 ft²?
About 100 tiles of 12 × 12 in, 225 of 8 × 8 in or 50 of 12 × 24 in, plus 10% waste.
How much extra tile should I buy?
10% for straight layouts, 15% for diagonal and 20% for herringbone, plus a box of spares for repairs.
Should I include the grout line?
Yes – on small tiles the joint noticeably increases the area each tile covers.
What formula does the Tile Calculator use?
Tiles = area ÷ ((tile L + joint) × (tile W + joint)) × (1 + waste).