Line styles

Use solid lines, dotted lines and dashed lines to differentiate between time series. This also means lines look more distinct when printed in black and white or if a user is colour-blind.

Axis labels and tick marks

Continuous data axes

For continuous data axes centrally align labels over tick marks.

Example of how to format continuous data axes

The x axis of a chart with the dates labelled on the tick marks, increasing by one year from 2000 to 2004.

Categorical data axes

For categorical data axes labels should be aligned between tick marks.

Example of how to format categorical data axes

The x axis of a chart labelled with category names placed between tick marks. Categories are Green, Blue, Red and Yellow.

Using more ticks than labels

You can use more tick marks than labels; ticks indicate the scale or level of detail of the data.

Label the final tick if there are more ticks than labels and there is space to do so.

Example of how to format ticks and labels

Economic inactivity rate for people aged 16 to 64 years
UK, January 1980 to October 2014

A line chart showing the inactivity rate for people aged 16 to 64 years, with dates on the x axis increasing every five years from January 1980 to October 2014.

Legends or keys

Using a legend or key

A legend or key should not be used, instead label the data directly. If a legend or key is necessary, place it on the chart as close as possible to the data.

Example of how to use a legend or key

Example of how not to use a legend or key

Order and orientation

The order and orientation of the legend or key should be the same as the data.

Example of how to order a legend or key

Example of how not to order a legend or key

Long category names

Using long category names

Use a horizontal bar chart rather than a vertical bar chart if your data have long category names.

Example of how to format a bar chart with long category names

Example of how not to format a bar chart with long category names

Subcategories

Labelling the subcategories

If the subcategories are not the same in all of the main categories, label the main categories and subcategories directly on the y-axis.

Example of how to label categories and subcategories

A rotated bar chart showing the ethnic group categories and their subcategories listed on the left-hand side.

Chart titles

Label charts as a figure and number them in order. Figures should have a main title and a statistical subtitle. Titles and subtitles should be concise and in sentence case.

Main title

The main title should be descriptive, and tell the trend of the data or highlight the main story. Try to limit the number of words to no more than 10. This should make the description easier to read and avoid the text wrapping onto several lines, especially on mobile devices.

If you need to add context or detail to the chart, use annotations or support with your analysis.

Statistical subtitle

The statistical subtitle should be as short as possible and must include the:

  • statistical measure
  • geographic coverage
  • time period

You do not need to include these elements in the subtitle if they are already in the main heading.

Writing chart titles to support your analysis

When writing your chart title and analysis:

  • use chart titles to complement or build on, but not repeat section headings
  • add further context and explanation of the chart’s message in your main text
  • do not try and summarise everything the chart says in the title, but prioritise the main message

Take care not to use language in a title that you would not use in your analysis. Exaggerated language such as “greatest rise ever” may be more eye-catching, but use sparingly as it may appear sensationalist or could potentially be misinterpreted.

It can be useful to draw attention to a record level being recorded in the most recent data, but if a new record continues to be set every month, using the same title will lose its impact. Use sparingly and find another message to concentrate on instead.

Examples of how to write chart titles and subtitles

A line chart showing the gender pay gap fell to 8.6% among full-time employees in 2018.

A line chart showing that motor trades continued a decline seen over the past 2 years to July to September 2019.

Line chart showing crime rates that homicides have increased over the last four years to year ending June 2018, following a long-term downward trend.

Your title can refer to a shorter period than shown on the chart. You can highlight an important short-term trend and give broader context by using a longer timeframe in your chart and analysis.

If your chart has more than one message

If a chart has more than one narrative, choose the one that will be most relevant to users for the main title. Use annotations to draw attention to secondary messages, but do not try and explain every nuance in the chart when your analysis can provide more detail.

Example of how to use annotations to draw attention to secondary messages

Line chart showing that the number of police recorded offences involving firearms has decreased in the latest year to year ending June 2018.

Titles for other visual elements

Other types of visual content can communicate information. If you are using a flow chart or a map, the same titling principles apply. Use a descriptive title to tell the user what the story behind the image is, and use a statistical subtitle if appropriate.

Example of how to write a descriptive title for visual content

An interactive data visualisation map showing that disposable incomes tend to be highest in the South East between 1997 and 2017.

Sometimes a graphic may genuinely be one you wish your user to explore – there is no immediate story or message on display. For example, some of the interactive graphics coming from the Data Visualisation team may be in this space. In these rare cases, it is acceptable to use a title that encourages the reader to explore the graphic.

Example of how to write a title for an exploratory tool

A data visualisation explorer tool that allows users to explore how well-being ratings have changed in their area.

Chart labels

Horizontal text

Chart text must be horizontal. If the labels will not fit into the required space, transpose the chart or convert the units.

Example of how to format text in a chart

Unemployed adults aged 16 to 64 years by region
England, 1993

Example of how not to format text in a chart

Unemployed adults aged 16 to 64 years by region
England, 1993

Right alignment of y-axis values

Your y-axis values should always be right-aligned to make them as easy as possible for users to read.

Example of how to align y-axis values

Pets by nation
UK, 2012

Bar chart showing pets by nation in the UK in 2012, with the y axis values right-aligned.

Labelling values in a chart

Use of data value labels

Bar charts should not need data value labels. If you need data value labels, create a chart−table combination.

Example of a chart−table combination

If you cannot create a chart−table combination, make sure the data value labels are placed at the base of each bar and right-aligned.

Example of how to format data value labels in a bar chart

Rotated bar chart showing goods and services categories listed down the left-hand side y axis.

Things to avoid

Avoid putting the values at the end of each bar, as this makes it difficult for users to follow and compare the values.

Example of how not to format data value labels

Annotation and footnotes

Using annotations

Chart annotations can be useful to tell your data’s story. They must be concise and immediately relevant, for example, to highlight important trends or dates on the chart that help the user understand the data. 

Place annotations on the chart as close as possible to the data points of interest. Avoid using too many annotations as this is likely to overwhelm users and reduce their effectiveness. We recommend only including three to four annotations per chart. 

The chart builder tool we use to create charts on the ONS website has a limit on the length and number of annotations that can be included and where they can be placed. They should be limited to around 50 characters (10 to 12 words) and be no more than one sentence. 

Using footnotes

Footnotes should be limited to important information needed for users to understand and interpret a chart or table. They should only be used to refer to the data specifically used in that chart or table. If a footnote refers to data used in general throughout the bulletin or article, this should be worked into the surrounding commentary instead. 

Avoid using too many footnotes as they can make the page long and interrupt the flow of the analysis, which is especially off putting for users on mobile devices.  

Footnotes should: 

  • be clear and concise 
  • spell out any acronyms used in the chart or table 
  • not include information that belongs in the main text 
  • avoid repetition of survey names  this should be included in the source 

Footnotes must be presented in context with the chart they relate toThey should not be placed in a separate section where they require the user to scroll up and down the page.  This is to ensure that if the chart is reused or if a user views only one chart, they get the information they need in order to understand the data. 

Example of how to use annotations and footnotes in a chart

Number of divorces1
England and Wales, 1910 to 2011

Footnotes (include at end of accompanying copy text)
1 Divorce figures include both decree absolutes and decrees of nullity

We are constantly improving based on research and best practice. Any significant changes to our guidance are available on the Updates page.