In the spirit of better investing, and in celebration of the first annual Worldwide Invest Better Day (WWIBD) coming up on September 25, Motley Fool analysts will be answering user- and reader-submitted questions leading up to the big event. "Ask a Fool" anything, and we'll do our best to help you invest better.

Market cap is one of the many metrics that investors can use to assess the size of a company. One share of the biggest company in the world, Apple (NASDAQ:AAPL), currently costs $668. To calculate Apple's market cap, simply multiply that number by the number of shares outstanding -- in this case, around 943 million -- and you get a market cap of roughly $630 billion. Watch the video below to learn more about calculating and interpreting a company's market cap.

 

Click the green button below to join the thousands of people celebrating Worldwide Invest Better Day on September 25!

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.