No matter what format your charts and graphs will be made in, using alternative text or captions to make them accessible to screen readers is essential. Your graphs and charts must also be easy to read and easy to understand.
Before adding captions and alt tags to your charts and graphs, figure out what the purpose of the graph is, what are the most significant points to the graph are, and what the order you describe the points in should be in.
Some graphs are easier than others to translate because their purpose is easy to state. Pie graphs' purpose is to state the percentages of a group of entries. This purpose is easy because you can just list off the entries and their percentages in a simple list.
You probably won't only use simple pie charts. When this is the case, lists will only confuse your audiences. In this example, each pie chart could be read like the first pie chart; however, the numbers couldn't be compared. That's why you should change the order and write comparisons of the two charts instead.
Writing the order of your caption as a comparison instead of a simple list makes this caption easy to understand and even helps imply more information.
Some graphs have extra information that doesn't enforce the point it is trying to prove. When this arrives, you do not have to write that superfluous information. In the alt tag or caption, write only the essential facts.
If in this population map, all that matters is that big cities have the highest population and that rural areas have the smallest populations, it doesn't matter if we state that 100-250 people per square mile live
in San Luis Obispo according to this map.
In the case of a complex diagram, write a description of it in your alt tag or caption. Be sure to have the purpose of the diagram in your head and do not be afraid of not describing unimportant information. Also describe the diagram in an understandable order.
Basically make sure that anyone could understand the diagram if it was read to them.
Make sure the colors of the chart or graph have enough contrast with each other to be read by people with seeing disabilities. Black and white have the most contrast.
Avoid using greens and reds together because people with color blindness can not tell them apart.
Do not use bold textures that make it hard to read the graphs.
