The Strange Coin Flipping Fact That Might Make Your Head Spin

Caitlin Schneider

Even if probability isn’t your strong suit, you can likely understand how in a basic coin flipping situation, it’s theoretically just as likely for you to turn up heads/heads as heads/tails. Except that that’s not actually true.

In the video above, Numberphile mathematician Dr. James Grime takes us through the cause behind the counterintuitive occurrence. Using 50 coins, he demonstrates how a random series of flips pretty closely matches the expected waiting time of heads/heads (six flips) and the expected waiting time of heads/tails (four flips). The reason heads/tails comes up more frequently has to do with uncounted consecutive values—we promise it makes sense—though at the end of the video, the team does concede that in their first go-around, the results played out in exactly the opposite way.

For a full understanding of the phenomenon, check out Grime’s lesson, and then get to work on perfecting your coin flip hustle.

[h/t Gizmodo]

Banner image: iStock

Know of something you think we should cover? Email us at