The centred layout guide
Equal edges.
One clear calculation.
This planner draws one straight grid in a rectangle. It uses the fewest positions that span each usable axis, keeps interior positions full size, and splits any end reduction equally.
All gap values are your inputs. The planner does not recommend grout spacing, perimeter gaps, installation methods or a cutting procedure. Its output is a geometric model to compare with your actual project and product requirements.
1. Keep the room, tile and gaps separate
Enter the complete rectangular room length and width in metres. Enter actual tile length and width in millimetres. The planner converts the room measurements to millimetres so every part of the layout uses one unit.
One perimeter-gap value is applied on all four sides. The interior-joint value applies only between neighbouring positions, so an axis with five positions has four interior joints. A single-position axis has no interior joints.
Tile length normally runs along room length. Turning the orientation swaps the tile dimensions; it does not rotate the room. The output dimensions always read along room length × room width.
2. Remove the perimeter gaps
Work on the length and width separately. If the full axis is R millimetres and your perimeter gap is P, the usable dimension U is:
One gap at each end of the axis.
A 3,000 mm room length with a chosen 10 mm gap has 2,980 mm between the gaps. If the two gaps consume the whole axis, there is no rectangle left to fill and the calculator rejects the input.
3. Count positions along each axis
Let T be the tile dimension on that axis and J your interior joint. A run of N full positions plus its N − 1 joints spans N × T + (N − 1) × J. The smallest position count that can span the usable dimension is:
The calculator uses exact decimal arithmetic for accepted inputs, rather than adding a rounding tolerance at full-tile boundaries. It accepts up to six decimal places per field; that arithmetic precision does not establish the accuracy of a physical measurement.
4. Balance the opposite edge pieces
If N is one, the single piece dimension is U. If N is two or more, N − 2 interior positions retain dimension T. Split the space left after those positions and all interior joints equally between the ends:
Both opposite edges receive that dimension. An edge dimension exactly equal to T is recognised as full size. If your joint value leaves a zero or negative edge piece, the planner reports an error instead of drawing an impossible layout.
Worked example: 3 m × 2.4 m
Use square 600 mm tiles, a chosen 3 mm interior joint and a chosen 10 mm perimeter gap. These are illustrative inputs for the arithmetic.
| Calculation | Along room length | Along room width |
|---|---|---|
| Full room dimension | 3,000 mm | 2,400 mm |
| After two 10 mm gaps | 2,980 mm | 2,380 mm |
| Positions, rounded upward | 2,983 ÷ 603 → 5 | 2,383 ÷ 603 → 4 |
| Interior full dimensions | 3 × 600 mm | 2 × 600 mm |
| Interior joints | 4 × 3 mm | 3 × 3 mm |
| Balanced edge dimension | 584 mm | 585.5 mm |
The result is five columns × four rows, or 20 laid positions. Six are full size; 14 have one or both dimensions reduced.
| Finished dimensions, length × width | Position type | Quantity |
|---|---|---|
| 600 × 600 mm | Full size | 6 |
| 584 × 600 mm | One dimension cut | 4 |
| 600 × 585.5 mm | One dimension cut | 6 |
| 584 × 585.5 mm | Two dimensions cut | 4 |
The length check is 584 + 600 + 600 + 600 + 584 + four 3 mm joints = 2,980 mm. The width check is 585.5 + 600 + 600 + 585.5 + three 3 mm joints = 2,380 mm. Adding the perimeter gaps restores the complete room dimensions.
When a boundary tile is full size
For a 1.203 m axis, 600 mm tiles, a 3 mm joint and no perimeter gap, two full tiles plus one joint span exactly 1,203 mm. The calculated edge dimension is 600 mm, so both positions are classified as full size. A position is not labelled a cut just because it touches the perimeter.
When there is only one position
A 0.45 m × 0.30 m rectangle with 600 mm tiles and a chosen 10 mm perimeter gap leaves one 430 × 280 mm position. There are no interior joints. Both tile dimensions are reduced, so the list calls it a two-dimension or corner cut. That label describes dimensions, not the number of physical saw passes.
Layout counts are separate from tile orders
A laid position is one rectangle in this model. It is not a promise that you can produce every piece from a minimum number of purchased tiles. Offcut reuse depends on the real pieces, cutting loss and the material; none of that is optimised here.
The model also excludes staggered, diagonal and decorative patterns, openings, fixtures, uneven walls, changing gaps, broken pieces and installation tolerances. It does not choose between alternative grid offsets or recommend a minimum edge size. The limit of 2,500 positions and 500 positions per axis is a display limit for this tool, not a project or installation limit.
Use the Tiletally box planner separately to combine areas, your chosen extra allowance and actual carton coverage. The tile ordering guide explains that calculation and the distinction between measured coverage and usable spares.
Save the version you checked
Download the piece list for the exact dimensions and quantities currently shown, or print the layout with its diagram. Inputs are held only in the current browser tab. Refreshing clears your changes; see the privacy notice for hosting and analytics details.
For a calculation issue, email the public forwarding address tiletally.sturdy964@aleeas.com with the measurements you entered. The contact page explains correspondence.