When to use a Donut Chart
You are showing parts of one whole
Revenue by product line, budget by department, traffic by channel. The segments must be mutually exclusive and add up to 100% of something real.
You have a few large categories
Two to five segments is where a donut works. The reader is comparing a small number of clearly different shares, which angles handle perfectly well.
The total is part of the message
The hole gives you a natural place for the headline number — total revenue, total respondents — so the chart carries both the total and its split without extra chrome.
One share is the story
"Nearly two thirds of revenue comes from one product" reads instantly as a ring. A donut is at its best when you want a single proportion to land, not when you want six compared.