Running out of tiles halfway through a job is a nightmare — you need to reorder and hope the same batch is still available. Ordering too many wastes money. Get the calculation right and you avoid both problems. Here's how to do it step by step.
Step 1: Measure the surface area
Start by measuring the area you want to tile. Calculate per rectangle or section. For L-shaped rooms, split them into two rectangles and add them together.
Also measure any cutouts (like a bathtub or toilet base) and subtract them from the total area.
Step 2: Add cut waste
You always need to account for cut waste — tiles you'll have to cut to fill edges and corners. How much waste you get depends on your laying pattern:
| Pattern | Cut waste | Notes |
|---|---|---|
| Straight / grid | +10% | Least cutting, great for beginners |
| Brick bond (offset) | +10% | Each row shifted by half a tile |
| Diagonal (45°) | +15% | More waste at the edges |
| Herringbone | +15–20% | Complex pattern, more offcuts |
| Irregular room shape | +20% | Many corners, alcoves, or pillars |
Step 3: Convert to number of boxes
Now that you know how many m² you need, convert that to boxes. The packaging always states how many m² each box covers.
💡 Always round up
Always round up the number of boxes. And always order 1 extra box as a reserve for future repairs. Tiles from the same batch may not be available later — even a slightly different batch can look different in colour.
Full example: a complete bathroom
Say you're tiling a bathroom of 2.5 m × 3.0 m in a straight pattern. The tiles are 30×60 cm and come in boxes of 1.62 m².
- Area: 2.5 × 3.0 = 7.5 m²
- Cut waste (10%): 7.5 × 1.10 = 8.25 m²
- Number of boxes: 8.25 ÷ 1.62 = 5.09 → 6 boxes
- Plus 1 spare box = order 7 boxes
📐 Calculate automatically with BuildExact
Enter your dimensions and BuildExact instantly calculates how many tiles, boxes and costs you need — including cut waste. Save it as a project and export as PDF for your client.
Download freeCommon mistakes when ordering tiles
- Skipping cut waste — the most common mistake. Always add it.
- Forgetting grout joints — wider joints (>3mm) reduce the actual tile area slightly. Factor this in for large-format tiles.
- Mixing batches — tiles with the same name but a different production batch can vary in shade. Buy everything at once.
- No spare tiles — always keep 1 extra box for future repairs.
Summary
The calculation is straightforward when you take it step by step: measure the area, add cut waste, and convert to boxes. Always round up and keep a spare box on hand.
Want to do this in seconds? With BuildExact, enter your dimensions and get the exact number of tiles, cost breakdown and a PDF summary — ready to send to your client.