We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

Is a Shuffled Deck of Cards Unique?

According to the laws of probability, it would be nearly impossible for any person to shuffle a deck of cards and have it end up in the same order as any other shuffled deck in history. This fact takes into account a deck of 52 properly shuffled cards, meaning that the cards were truly shuffled in order to create randomization. For example, a perfect shuffle — in which a deck is separated exactly in half and all of the cards are alternatively interlaced in order — is commonly used for magic tricks and would not have randomization. It is commonly accepted protocol that a deck of cards requires seven shuffles to have proper randomization.

More about probability:

  • A two-sided coin might not have an equal chance of landing on each side after being flipped. Research has suggested that 51% of the time, the coin will land with the same side up as when it was flipped.

  • In a group of 23 people, there is a 50% chance that two of them will have the same birthday.

  • It would take about eight perfect shuffles of a deck of cards to get it back to its original order.

Discussion Comments

By anon346441 — On Aug 28, 2013

This statement requires, begs, a statement of what the odds are. As stated, and then followed by the statement about 8 perfect shuffles to return to a perfect order, seems counter-intuitive and less that logical.

By anon346422 — On Aug 28, 2013

If a deck returns to its original not order after eight perfect shuffles, then on that eighth shuffle it would be returning to the same order as a previous(the first)deck. That's a contradiction.

By anon346383 — On Aug 28, 2013

I have never understood any reasoning - mathematical or otherwise - why it's a 50 percent chance of two people in a group of 23 sharing the same birthday. As far as I'm concerned there are 365 days in a year and therefore a one in 365 chance of it being any day. The next person has 363 chances about it being different against one the same and so on. Assuming the 22 previous were different, why doesn't the 23 have 342 chances for it to be different and 22 the same or about 17 to 1?

WiseGEEK, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGEEK, in your inbox

Our latest articles, guides, and more, delivered daily.