House of Commons Library guide to designing effective charts

Charts are by their nature more subjective than tables. A chart works on visual and different analytical levels and is open to a greater degree of interpretation. There are far more options to choose from covering types of chart, colour, size, dimensions, labelling, scales etc. Therefore there are a limited number of hard and fast rules covering every situation where you need to use a chart.

This is not to say that there are no rules to follow or that ‘anything goes’ when putting a chart together. A poor chart can be confusing, boring, misleading or all three. A good chart can reach your audience in ways that a table or description in text cannot; helping them to quickly understand important trends and patterns and to make comparisons -even complex ones- quickly , without much ‘work’ on their part and to remember them and the key message you are making.

This guide includes some general principles to think about when putting a chart together. It also gives some ‘default’ options for charting different types of data. These will often be starting points only and can be improved on -better suited to your audience or characteristics of the data- with further refinements.

The guide begins by setting out some key areas to consider before even starting your chart. It then defines the terminology used for different elements of a chart, lists major chart types and sets out general principles of a good chart. As chart type is so important the next section gives some information to help chose which type to start with. The remainder of the guide is split between applying general charting principles to each component part of a chart and some further areas to consider where we could make improvements. This last section is intended to be thought provoking not prescriptive.

All the examples in the guide are created in Excel. The tips, suggestions and refinements are applicable to a chart created with any software, but as some are particularly focused on overcoming the drawbacks of Excel charts they will be more relevant to someone creating a chart in Excel. However, this guide is not a step-by-step guide to creating a chart in Excel.

It does not look specifically at stylistic elements relating to ‘branding’ -colours, typeface, font size, line styles etc. and is therefore applicable to any brand style. The examples and illustrations in this guidance all use the Library’s new 2020 style.