How to calculate tile cuts and build a cut list
Area ÷ tile size is not a cut list. Here is how to plan every edge piece, avoid thin slivers, and order the right number of boxes before the first cut.
Most “how many tiles do I need?” calculators divide area by tile area and add 10%. That number is useful for a rough budget. It is not a plan for installation. Cuts land where the grid meets walls, openings, and out-of-square corners—and those pieces decide whether the job looks intentional or patched.
A cut list is the difference between guessing on site and buying with a known set of edge sizes. Below is a practical way to calculate tile cuts before you order boxes, plus how a scaled 3D layout (like Layometry) makes the thin slivers visible while you can still change the starting line.
1. Why “area ÷ tile + 10%” fails for cuts
Area methods ignore grout pitch, pattern offset, and where the grid starts. A one-millimetre change in joint width shifts the last piece on a long wall. A centred layout can turn two ugly 40 mm strips into two workable 80 mm pieces—or the opposite.
Waste percentage also hides risk. Ten percent may cover straight floors with few openings. It will not cover herringbone, diagonal lays, or a bathroom full of niches. You need the list of piece sizes, not only a box count.
- Budget from area; install from geometry.
- Grout is part of the module size.
- Pattern and start line move every edge cut.
2. Measure the finished surface, not the rough opening
Use finished dimensions: after plaster, boards, or waterproofing where relevant. Record width and height for each wall; for floors, record the outline, including L-shapes and alcoves. Note doors, windows, niches, and fixed obstacles.
Out-of-square walls matter. If the wall is wider at the top than at the bottom, a level tile grid will create wedge-shaped edge cuts. Measure both ends of each run so the plan matches how a tiler actually works from a baseline.
- Finished size beats rough opening.
- Capture openings before you lock the layout.
- Check both ends of long walls for squareness.
3. Build the true module: tile + joint
The repeating step along a wall is not the tile face alone. It is tile width plus grout (and the same on the other axis). That module decides how many full tiles fit and what remains at the end.
Use the real calibre from the box when you can. A “600 mm” tile is often slightly different; the joint you plan to use must match the spacers on site. Lock tile size, joint width, and units (mm or inches) before comparing patterns.
4. Choose pattern and starting axis before you count cuts
Straight lay is the easiest cut list to predict. Running bond shifts every other row and changes end pieces. Diagonal and herringbone increase triangular and angled cuts and need extra material.
Decide where full tiles should sit: centred on a feature, full tile at a visible corner, or balanced edge cuts on both sides. Dry-fit or use a scaled planner. The goal is no knife-thin slivers on a visible edge—many installers avoid pieces much under about a third of the tile width when they can.
- Compare at least two start lines.
- Reject layouts that leave thin visible strips.
- Complex patterns need more allowance and more time.
5. Turn the layout into a cut list (not a vague waste %)
Walk every edge and opening. For each partial tile, write the finished cut size. Then group identical sizes: shops and on-site cutting go faster when you cut five 142 mm pieces together instead of measuring each one against the wall.
Add a small breakage buffer after you know the geometry—not instead of it. Keep leftovers that can become opposing cuts when the pattern allows. Export a CSV or printed schedule if you work with a helper or a cutting station.
- One row per unique cut size and count.
- Mark which surface / elevation each cut belongs to.
- Buffer comes after the list, not instead of the list.
6. Verify in a scaled planner before you buy boxes
A 3D or scaled plan shows what a spreadsheet cannot: how joints meet at corners, whether a niche forces an awkward piece, and how many full tiles you actually need. Adjust offset or rotation, then regenerate the cut list.
Layometry is built for this step: enter room and tile sizes, set grout and pattern, and see every cut at real size in the browser—then export a cut list and PDF when you are ready to order. No install required; guest projects stay in the browser until you sign in.
Try it on your room
Open the free planner, enter one wall or floor, and generate the cut list before you pay for boxes. If a layout creates thin edges, move the starting line until the edge pieces look installable—then buy to that plan.
Conclusion
Calculating tile cuts means treating the surface as geometry: finished measures, tile-plus-joint modules, a chosen pattern, and a grouped list of edge sizes. Area rules of thumb are for budgets; cut lists are for installation.
Lock the layout before the first cut. A few minutes in a planner is cheaper than an extra box—or a visible sliver you cannot hide.