Surface Estimating
Tile Calculator
Accurately estimate the number of tiles, boxes, and total area for your tiling project. Include grout joint width for precise piece counts and factor in professional waste allowances for pattern alignment.
Tile Calculator
Estimate tiles and boxes for a rectangular floor (minus openings) with grout and waste
Results
Enter values above to calculate
Calculating with Grout Joints
The "working" size of a tile includes the width of the grout joint. This is critical for calculating how many physical pieces are needed to fill a room.
Recommended Grout Widths
| Tile Type | Joint Width | Design Rationale |
|---|---|---|
| Mosaic / Small format | 1.5 mm (1/16") | Keeps focus on tile detail |
| Standard Wall / Floor | 3.0 mm (1/8") | Industry standard for rectified tile |
| Large Format (60cm+) | 5.0 mm (3/16") | Allows for substrate variations |
| Natural Stone / Rustic | 6.0 mm+ (1/4"+) | Compensates for irregular tile edges |
Step-by-Step Formulas
1. Net Installation Area
Measure the floor or wall area to be tiled. Subtract areas for cabinets, tubs, or accent features that will use different materials.
2. Waste Factor
Add 10% waste for standard grid patterns. For diagonal layouts, herringbone, or complex patterns, budget 15–20% to account for more cut tile loss.
3. Individual Tile Area
The calculator includes the grout joint width in the area calculation of each tile. This gives a more accurate count of how many pieces fill the total area.
4. Box & Piece Counts
The total required area is divided by the sloped area of one tile. This provides the total number of pieces. If you enter the pieces-per-box value, the calculator will round up to the next full box.
Worked Example
Bathroom floor: 3 m × 2.4 m area, 300 × 300 mm tiles, 3 mm grout joint, 10% waste. 12 pieces per box.
Why Tile Orders Run Short
Tile is the material most often re-ordered mid-job, and the reasons are consistent:
- Grout Joints Change the Module: A 12 in tile with a 1/8 in joint occupies 12.125 in of floor. Over a large room that difference removes most of a box from the count, which is why the joint belongs in the calculation.
- Boxes, Not Tiles, Are What You Buy: Tile ships by the box with a fixed coverage. Converting your area to whole boxes tells you the real order and shows how much spare you will end up holding.
- Dye Lots Do Not Repeat: Ceramic and porcelain shade varies between production runs. A top-up box from a different lot can be visibly different, so buy the full quantity, including attic stock, in one order.
Benefits of Using This Calculator
Example Calculations
Three scenarios worked through step by step:
Example 1 — Straight Lay Floor
Room 14 ft × 12 ft, 12 × 12 in tile, 1/8 in joint, 10% waste.
Module = (12 + 0.125)² = 12.125 × 12.125 = 147.0 in² = 1.021 ft²
Area = 14 × 12 = 168 ft²
Tiles = 168 ÷ 1.021 = 165
With 10% waste = 165 × 1.10 = 181.5 → 182 tiles
At 15 tiles/box = 12.1 → order 13 boxes
Example 2 — Diagonal Layout
Room 10 ft × 10 ft, 18 × 18 in tile, 3/16 in joint, 20% waste for diagonal cuts.
Module = (18 + 0.1875)² = 330.8 in² = 2.297 ft²
Area = 100 ft²
Tiles = 100 ÷ 2.297 = 43.5 → 44
With 20% waste = 44 × 1.20 = 52.8 → 53 tiles
Diagonal layouts cut every perimeter tile at 45°
Example 3 — Bathroom With Openings
Room 8 ft × 6 ft, 12 ft² of fixtures deducted, 12 × 24 in tile, 10% waste.
Gross area = 8 × 6 = 48 ft²; net = 48 − 12 = 36 ft²
Module = (12.125 × 24.125) ÷ 144 = 2.031 ft²
Tiles = 36 ÷ 2.031 = 17.7 → 18
With 10% waste = 19.8 → 20 tiles
Result: 20 tiles, plus one spare box as attic stock
Ordering Tip
Ordering Tip
Buy one extra box beyond your calculated need and store it. Tile gets cracked by dropped objects years after installation, and a matching replacement from the original dye lot is the difference between an invisible repair and re-tiling the whole floor.
Frequently Asked Questions
- How much extra tile should I buy?
- 10% for straight patterns, 15% for diagonal or complex patterns like herringbone.
- Does the calculator include grout joints?
- Yes, it adds the grout joint width to the tile dimensions to provide an accurate piece count.
- What is a "Die Lot"?
- Batches of tile made at different times can vary in color. Order your entire project at once from the same batch to ensure a perfect match.
- How much extra tile should I buy?
- Ten percent over the measured area for a straight layout, 15–20% for diagonal or herringbone patterns, and more for rooms with many alcoves. On top of that, keep one full box as attic stock for future repairs — dye lots do not repeat.
- Do grout lines really affect the tile count?
- They do, and in your favour. A 1/8 in joint on a 12 in tile means each tile occupies 12.125 in, so you need slightly fewer tiles than the bare area suggests. On large-format tile with wide joints the effect is worth several tiles.
- What size grout joint should I use?
- One-sixteenth to 1/8 in for rectified porcelain, 1/8 to 3/16 in for standard ceramic, and 3/16 to 1/4 in for natural stone or handmade tile with size variation. Larger tiles generally need slightly wider joints to absorb dimensional tolerance.
- How many 12x12 tiles are in a box?
- Usually 15 to 17, covering roughly 15 square feet, but it varies by manufacturer and tile thickness. Always order by box coverage rather than tile count, since that is how the product is priced and palletised.
- Should I tile under appliances and cabinets?
- Tile under freestanding appliances so they sit level and can be pulled out for service. Under fixed base cabinets it is usually skipped to save material, though tiling the full floor makes a future kitchen change far easier.
- How much thinset and grout will I need?
- Roughly one 50 lb bag of thinset per 40–60 ft² for standard tile with a 1/4 in notched trowel, and less coverage for large-format tile needing a deeper notch. Grout depends on joint width and tile size; the bag chart gives coverage per square foot.
- Can I mix tiles from different boxes?
- Yes, and you should. Open several boxes and lay from them in rotation so any slight shade variation is distributed evenly across the floor rather than appearing as a visible block of off-colour tile in one area.