How to Write Alt Text for Graphs, Charts, and Diagrams for Math and STEM Content

Today’s post is for our math and STEM teachers and professors. Alt text helps students using screen readers understand visual content in math and science. When writing alt text, describe what’s on the screen without giving away answers. Stick to the facts: what kind of chart it is, what’s on the axes, what labels or values appear, and let the student do the rest.

This guide covers how to write alt text for line graphs, bar charts, pie charts, scatter plots, diagrams, and flowcharts. It also includes a checklist and a tool that can help make math documents accessible.

Video Guide

Line Graphs

Start by naming the chart as a line graph. Describe the coordinate plane and give the range for the x- and y-axes. Mention any units if they’re there. List key points where the line crosses. If the graph shows more than one line, label each one using the information in the chart, like color or name. Don’t explain what the line means or how steep it is.

Example:
Line graph on a coordinate plane. The x-axis runs from 0 to 6. The y-axis runs from 0 to 10. A straight line passes through the points (2, 3) and (5, 9).

This gives the structure and numbers without solving anything for the student.

Bar Charts

Say it’s a bar chart, and give the labels and values for each bar. Don’t say which bar is the tallest or make comparisons. If the chart has groups of bars, describe each group and its values. Mention color only if the question brings it up.

Example:
Bar chart showing exam scores by subject. Math: 78. Science: 85. History: 90. English: 74.

This lets students do the comparing themselves.

Pie Charts

Start with the type of chart and what it’s showing. List each slice with its label and percentage. Skip comments about size, just give the numbers. Don’t mention color unless the chart or question calls it out. If the chart is complicated, consider using a table or longer description instead.

Example:
Pie chart of household energy sources. Gas: 50 percent. Electric: 30 percent. Solar: 15 percent. Other: 5 percent.

Scatter Plots

Say it’s a scatter plot and include how many data points it shows. Give the x- and y-axis ranges. Point out areas where the dots are more clustered or spread out. If some dots stand out or fall in a tight range, describe that. Don’t say there’s a trend or correlation, just describe what’s visible.

Example:
Scatter plot with 20 data points. The x-axis ranges from 0 to 10. The y-axis ranges from 10 to 70. Points are spread out, with most between x = 4 to 9 and y = 20 to 50.

This shows what’s on the page without doing the analysis.

Diagrams

Describe the figure using neutral terms. If it’s a shape, count the sides instead of naming it (unless the name is given). Mention any labels, side lengths, or angles. The goal is to give the structure without solving the problem for the student.

Example:
A closed figure with five straight sides. One side is labeled 6 centimeters. One angle is labeled 120 degrees.

Flowcharts

Start by saying it’s a flowchart. List the boxes in order and what each one says. Mention arrows or connections if they show order. Don’t explain how the process works, just list the steps as written.

Example:
Flowchart with three boxes connected by arrows. Labels read: Start. Process. End.

Quick Checklist

• Name the type of chart or diagram
• Give axis ranges, labels, and units
• List visible values or points
• Skip interpretations or comparisons
• Use labels from the image
• Avoid color unless required
• Write longer descriptions if needed for complex visuals
• Keep the tone factual and clear

Making Math Content Accessible

If you’re working with a lot of math content in PDFs, DocAccess can help. It converts math to MathML, which screen readers can read out loud. You upload a file, and with one click, it displays the math in an accessible format. This helps schools and organizations meet accessibility requirements quickly and efficiently.

Let me be your champion for inclusion. I offer tailored solutions (and self-paced courses!) to ensure your documents meet and exceed compliance expectations. For more detailed insights, tutorials, and in-depth discussions on accessibility and related topics, don’t forget to check out my YouTube channel: The Accessibility Guy on YouTube. Subscribe for regular updates!