What this planner works out
This planner divides your area by your tile size to give a grid of columns and rows, calculates the minimum tiles and the quantity to buy with waste, and flags the edge cuts the layout will produce.
The edge cut information is the useful part. A layout that leaves a 4 cm sliver along a visible wall looks poor however well it is tiled, and knowing that before you start lets you centre the layout instead.
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Before you plan
- Measure in centimetres, and measure the area at several points. Walls and floors are rarely square.
- Tile dimensions should be nominal size. Grout joints add 2 to 5 mm per tile, which the calculator does not model.
- Allow 10% waste as a minimum, 15% for diagonal layouts and 20% for patterned or herringbone arrangements.
- Decide which edges are visible. Cuts should be pushed towards the least-seen edges.
Corners are rarely square and starting there sends the error along the whole run, ending in a tapering cut on the opposite side. Setting out from a centre line and working outwards splits the error into two matching cuts at each edge, which reads as deliberate rather than as a mistake.
How this calculator works
A grid, then a quantity, then the remainders:
Columns = area width ÷ tile width, rounded up
Rows = area height ÷ tile height, rounded up
Minimum tiles = columns × rows
Buy = minimum × (1 + waste ÷ 100), rounded up
Edge cuts = the remainders of each divisionRounding both divisions up assumes every partial column and row needs a cut tile. The remainders show how wide those cuts will be.
The calculation ignores grout joints. Over a run of eight tiles with 3 mm joints that is 24 mm, which is enough to change whether a final cut is comfortable or awkward — worth allowing for on tight areas.
Worked example: a 240 by 220 cm area
Using the default figures — a 240 by 220 cm area in 30 by 60 cm tiles with 10% waste:
- Layout: 8 columns × 4 rows
- Minimum tiles: 32
- Buy with waste: 36 tiles
- Edge cuts: full width fit horizontally, 40 cm cut top or bottom
The width divides exactly, which is fortunate. The height leaves a 40 cm strip — two thirds of a tile, which is a comfortable cut. Had it left 5 cm instead, the sensible response would be to start half a tile lower so the remainder splits into two 32.5 cm cuts at top and bottom, which looks intentional. That decision has to be made before the first tile goes down.
Common mistakes
- Starting from a corner. Set out from a centre line so cuts are balanced.
- Ignoring grout joints. They accumulate across a run and shift the final cut.
- Putting the narrow cut on the most visible edge. Plan which edge takes it.
- Assuming the room is square. Measure diagonals and check before setting out.
- Buying too few for a patterned layout. Herringbone and diagonal layouts waste far more than 10%.
Frequently asked questions
How do I centre a tile layout?
Find the centre of the area, then dry-lay tiles outward from it to see what the edge cuts will be. If a cut comes out very narrow, shift the whole layout by half a tile so the remainder splits evenly between the two edges. Snap a chalk line or fix a batten on the set-out line and tile from there rather than freehand.
How much waste should I really allow?
10% for a straight layout in a simple rectangular area; 15% for diagonal; 20% or more for herringbone or a patterned arrangement. Add more for small rooms with many obstacles, because the ratio of cuts to whole tiles rises sharply as the area shrinks. Large format tiles also break more often when cut.
What size grout joint should I use?
Typically 2 to 3 mm for rectified porcelain and 3 to 5 mm for standard ceramic. The tile manufacturer usually specifies a minimum. Larger joints accommodate variation in tile size, which matters for handmade and natural stone tiles where dimensions vary noticeably between pieces.
Can I tile over existing tiles?
Sometimes, if the existing tiles are sound, well bonded and flat, and the substrate can take the additional weight. It raises the surface by around 15 mm, which affects door clearances, skirtings and worktop junctions. On floors, the extra height and weight need more careful thought, and lifting the old tiles is often the better option.
Is what I enter stored?
No. Measurements are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — building regulations guidance on floor loading and finishes
- Health and Safety Executive — controlling silica dust when cutting tiles
Sources are checked at publication and can change — how I choose and check references.