This entry is part of the Chart Index, the reference library for the Chart Design Field Guide.

A tilegram rebuilds geography from equal-sized tiles. Each region receives a number of tiles proportional to a measure, while the layout preserves enough relative position and neighbourhood to remain recognisable as a map.

It is also called a hex cartogram when hexagons are used. Unlike a choropleth, land area has no visual weight. Unlike a Dorling cartogram, the units are discrete and countable.

What it is

Every tile has the same area. The number of tiles assigned to a region carries the weight, while colour encodes the measure and direct labels identify the region.

The hero chart above is a thirty-tile Australia, each state's cluster sized roughly to its population — seven hexagons for New South Wales, one each for Tasmania and the ACT — and coloured by median weekly rent. The arrangement is authored rather than calculated from boundaries: regions remain broadly north, south, east or west of one another, but exact shapes, distances and coastlines are intentionally discarded. What the reader gains is that the ACT, a speck on any real map, is now a tile as big as any other and can be seen to be the second most expensive place in the country to rent. Randomise the rents and the clusters recolour in place; the tile count never changes, because it is the design, not the data.

When to use it

  • Geographic area would distort the importance of the measure.
  • Values can be expressed as a useful number of equal units.
  • Readers need to count or compare regional representation.
  • Broad position and adjacency matter more than precise boundaries.
  • A conventional map would leave small regions difficult to see or select.

When not to use it

  • Exact locations, boundaries, routes or distances matter.
  • Values require more precision than a practical tile count can provide.
  • The geography is unfamiliar and the simplified arrangement would be difficult to recognise.
  • Small differences would require hundreds or thousands of tiles.
  • The tile allocation would imply false precision after aggressive rounding.

Design principles

Give every region a place to be seen

The tilegram's first job is fairness of attention. On a real map of Australia the two territories and Tasmania together cover less than a fiftieth of the canvas, and whatever colour they carry is lost. The pair below is the hero's data on real boundaries and on tiles.

Median weekly rent as a choropleth
Western Australia's dark fill dominates the picture because Western Australia dominates the continent. The ACT — second most expensive in the data — is a dot the reader has to hunt for, and its label does not fit.
The same rents as a tilegram
Every region has at least one tile and a label. The ACT sits as a dark hexagon east of New South Wales, Tasmania is a pale one below Victoria, and Western Australia's cluster is about the size its population warrants rather than the size of its desert.

Make every tile equivalent

Each tile must represent the same quantity. State the unit clearly and use a rounding method that can be explained. If one tile represents a million people, it must do so everywhere in the map — and if the allocation is one tile per region regardless of population, that too is a design statement the reader must be told.

One tile per region: equal representation
The same rents on a layout that gives every state and territory exactly one hexagon. The map is now a ranking device — eight equal cells in roughly geographic order — and it says nothing about how many renters each colour stands for. Honest if the subtitle says so; misleading if it does not.

Preserve the geographic skeleton

Keep regions in familiar relative positions and preserve important neighbours where possible. A tilegram is distorted geography, not a freely arranged waffle chart. In the layouts here the Territory stays north of South Australia, Queensland north of New South Wales, and Tasmania hangs below Victoria; the reader who knows the country can find every state without reading a label.

Choose the resolution deliberately

Too few tiles flatten meaningful differences. Too many create clutter and make the map difficult to scan. Choose a unit that preserves the important comparisons while keeping the complete map legible at its intended size. Thirty tiles, as in the hero, keeps New South Wales and Victoria visibly different without turning the map into a mosaic; a one-tile-per-million-people layout would need twenty-seven and lose the territories.

Prefer hexagons when neighbourhood matters

Hexagons have six neighbours and reduce the strong horizontal and vertical alignment created by squares. This often makes irregular geographic arrangements feel more natural, although square tiles remain useful when the layout needs a strict grid.

Label regions directly

Boundaries and familiar silhouettes have been removed. Use concise region abbreviations within the layout and provide full names in tooltips. Colour should support identification rather than carry the primary quantity — or, when colour does carry the quantity, as here, the labels are the only thing that makes the map a map.

Without labels: a pattern, not a map
The same tiles with the region codes removed. A reader who knows the layout can still find New South Wales; anyone else is looking at coloured hexagons. On a tilegram the label is not decoration — it is the geography.

Explain rounding and omitted regions

Very small values may round to zero tiles. Decide whether to guarantee every region at least one tile, use a separate symbol, or disclose the omission. The choice affects both fairness and interpretation. The hero's layout guarantees a tile to the ACT and Tasmania, which over-represents both by population; the subtitle says "roughly proportional" for that reason.

Anatomy

The composition of a tilegram
An anatomical guide

A tilegram combines five elements:

  • Equal-area tile — one consistent visual unit.
  • Tile allocation — the count assigned to each region.
  • Geographic arrangement — an authored approximation of position and adjacency.
  • Region identifier — colour, abbreviation or both.
  • Unit statement — the quantity represented by each tile.
  • Cartogram — uses continuously scaled circles or polygons rather than countable equal tiles.
  • Waffle chart — uses equal tiles without a geographic arrangement.
  • Hexbin and H3 map — aggregates point observations into spatial bins rather than allocating tiles to administrative regions.
  • Choropleth — preserves geographic boundaries and encodes a normalised measure with colour.
  • Geographic base map — preserves actual geometry when location and shape matter.

Reading list

  • Raisz, E. (1934). The Rectangular Statistical Cartogram.
  • Nusrat, S. and Kobourov, S. (2016). The State of the Art in Cartograms.
  • Meirelles, I. (2013). Design for Information.