Chart Legends
Legends are keys for chart categories or series. Where possible, direct labels can reduce lookup effort; when a legend is needed, its labels and symbols should map clearly to the data.
Use a chart legend when readers need a key for series or categories and direct labels are not practical. Keep legend labels concise and make each label-symbol pairing unambiguous.
Key details
Important caveats
Direct Label Boundary
Prefer direct labels where they can identify series clearly without clutter; use a legend when direct labelling is not practical.
Placement Boundary
Legend placement is a design-system convention rather than universal grammar; ONS specifies an above-chart, left-aligned placement for its own charts.
Further guidance
Labels
Keep legend labels concise and make the symbol or line treatment clearly correspond to the category it identifies.
Practical Application
Use a legend when readers need a key to distinguish series or categories and direct labels are impractical. Keep each legend term short, pair it unmistakably with its symbol or line, and place the legend where the eye can connect it with the plotted data without excessive scanning.
Reader Check
Can each series be identified quickly, and would direct labels reduce lookup effort without making the chart crowded?
Worked Example
For a four-line time series, use a compact legend with four unambiguous series names if labels cannot fit beside the lines; for two widely separated lines, direct labels at the line ends may remove the need for a legend.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Chart elements — ONS Service Manual (opens in a new tab)Office for National Statistics · When to use chart legends versus direct labels and how legend labels/symbols are organized
- Chart typography — ONS Service Manual (opens in a new tab)Office for National Statistics · Typography and roles for chart legends, direct category labels and direct numeric data labels