Data visualisation style guide
This guide covers how I make charts and maps. It sets out the rules I follow, the colours and type I use, and the reasons behind each choice. You can apply it as it stands to your own work, or take it as a starting point and adapt it into a guide of your own.
Start with the principles Open the colour picker
How this guide is organised
The guide puts what to do first and why second.
| Section | Use it to |
|---|---|
| Principles | Check if a visual is ready to publish. |
| Planning | Write a brief, size up your audience and pick a format: a number, a chart, a map or a table. |
| Colour and Typography | Pick colours and type. |
| Big numbers | Show one key number at a glance. |
| Charts and Maps | Lay out a chart or map, choose a type and keep within its limits. |
| Dashboards | Combine numbers, charts and maps on one screen that people check regularly. |
| Make your own | Adapt this guide to another brand or organisation. |
| Background | Read the research behind the rules: perception, cognitive load, colour science and typography. Optional. |
Four kinds of notes recur throughout:
A firm rule. Break it only when you can explain why.
A common mistake, and what to do instead.
What to change, and where to start, if you are building a guide for your own brand.
A short reason, with a link to the background reading.
The short version
If you read nothing else:
- One visual, one message. Write the message as the title: “Incidents fell by a third after the ceasefire”, not “Incidents per month”.
- Put what, where and when in the subtitle: units, categories, period and place.
- Pick the simplest form that shows the message. Use a big number for one fact, a horizontal bar chart for comparing categories, and a line chart for a trend. Use a map only when location is the point.
- Label directly. Put labels on the data, not in a legend, wherever they fit.
- Use colour on purpose. Use one colour, plus grey for everything that isn’t the story. Add more colours only for real categories.
- Never use colour alone. Add labels, position, shape or line style.
- Remove what doesn’t help. No borders, 3D, shadows or heavy gridlines.
- Check it at the size people will see it, on screen and in print.
Pre-publish checklist
- The title states the takeaway, and the subtitle gives units, period and scope.
- The chart or map type matches the message (chooser).
- Axes and scales are honest: bars start at zero, and any cut axis is clearly marked.
- Data is labelled directly, with a legend only where direct labels don’t fit.
- Colours come from the palette, and the visual still reads in greyscale.
- Text is the house typeface, at least 9 pt in print.
- The source is credited, and notes explain any data limitations.
- Someone who wasn’t involved can state the message in one sentence.