Accessible Charts with Excel and Power BI

Making charts and reports more accessible

We all have a responsibility to ensure that our data is understandable by everyone. That includes people with disabilities. Charts and reports must be accessible for users with a range of abilities.

Many different disabilities can impact how someone interacts with information. Disability is more than a person's health condition; it's about exclusion through mismatched interactions. Simple changes to our designs improve our ability to communicate our stories.

Types of accessibility issues

Many different types of accessibility issues can prevent people from accessing and understanding visual information.

Exclusion through accessibility can be permanent (such as the loss of a limb), temporary (for example, a broken arm) or caused by their current situation (such as their surroundings). As a result, many more people benefit from improved accessibility than you might think.

There are several accessibility types to consider. These include:

Visual

Sight loss is a spectrum rather than all or nothing. Many people need corrective lenses; some will find it difficult to read in low light; others will have very low vision.

Additionally, many people (around 8% of men and 0.5% of women) are colour "blind". They have a colour vision deficiency that causes difficulty distinguishing between shades of colour.

Mobility

Mobility disabilities can include physical and neurological impairments that can make it impossible or difficult for someone to move their body in specific ways. People with a mobility disability will access your reports differently than how you might expect. For example, someone might not use a mouse for navigation and rely on solely a keyboard.

Understanding

There are around 300,000 employees in the UK alone with a learning disability. In addition, there are many people with learning difficulties (rather than disabilities), such as dyslexia. All of us can improve how we communicate our stories better.

General accessibility tips

• Use fewer categories. Reducing the number of categories can make your charts easier to interpret and reduce the number of colours you need. That makes the chart easier for people with colour-blindness or visual impairments.
• Or consider a different chart type. Some visualisations can become cluttered with more than a small number of categories. Consider, for example, changing from a pie chart to a vertical bar chart if you have many categories.
• Set Alt text for your charts. Both Excel and Power BI allow the alternative text to summarise the visualisation. Provide enough text to describe the visualisation's critical information but keep it as short as possible.
• Label your categories in place rather than with a separate legend - this makes the charts simpler for the user to interpret and reduces the need to translate colours to categories.

More accessible Excel charts

• Add axis titles to make the chart easier to understand. Adding axis titles allows removal of repetitive symbols from the values in the axes.
• Add data labels or callouts. Add values directly into the chart rather than relying on the axis. These can configured and styled to include different values (such as the series name). Also, consider removing individual values to remove clutter.
• Use symbols for data elements instead of (or in addition to) colours. Excel has various marker types (squares, circles, diamonds, etc.). Consider increasing the default size of these markers.
• Check for issues. Excel can automatically check your file for common accessibility problems (File / Info / Check for Issues / Check Accessibility).

More accessible Power BI reports

• Dynamic alt text. Conditional formatting and DAX measures allow alt text to be updated dynamically based on what the user has selected. Updating the alt text is particularly useful for people using screen readers.
• Avoid disabling "show data". There are various techniques to restrict users' access to data, but these can make interpreting the data harder for some users. Instead of disabling the ability to show the underlying data, consider pre-aggregating or anonymising the data if you need to keep it confidential.
• Configure the tab order for your visualisations to improve the user experience with assistive technologies (for example, when using the keyboard to navigate between visualisations). Also, remove decorative elements from the list of tab stops.

What do you think?

If you have any comments or suggestions for further tips, please get in touch. I'd love to hear from you. Thanks for reading.

Stephen Simmons is responsible for technical strategy and platform architecture at viewpointbi.com. He leads the software development team and writes regular articles on data and technology.