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 value, while colour and direct labels identify the region.
The arrangement is authored rather than calculated from boundaries alone. Regions remain broadly north, south, east or west of one another, but exact shapes, distances and coastlines are intentionally discarded.
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
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 100,000 people, it must do so everywhere in the map.
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.
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.
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.
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.
Anatomy
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.
Related types
- 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.