## How many perfect shuffles does it take to reset a deck?

If one can do perfect in-shuffles, then 26 shuffles will reverse the order of the deck and 26 more will restore it to its original order. . However, only 6 faro out-shuffles are required to restore the order of a 64-card deck.

## Is it possible to shuffle cards the same way twice?

The chances that anyone has ever shuffled a pack of cards (fairly) in the same way twice in the history of the world, or ever will again, are infinitesimally small. The number of possible ways to order a pack of 52 cards is ’52! ‘ (“52 factorial”) which means multiplying 52 by 51 by 50… all the way down to 1.

**How big is 52 factorial?**

52! is approximately 8.0658e67. For an exact representation, view a factorial table or try a “new-school” calculator, one that understands long integers.

**How many times do you need to shuffle cards?**

Jim Reeds at Bell Laboratories and showed that a deck is perfectly mixed if it is shuffled between 5 and 20 times. Next, Dr. Diaconis worked with Dr. Aldous and showed that it takes 5 to 12 shuffles to perfectly mix a deck.

### How many shuffles is a perfect shuffle?

The article caused one my colleague and fellow blogger, Rob Pratt, to ask if I was familiar with a bit of shuffling trivia: if you perform a perfect riffle shuffle, the cards return to their original order after exactly eight perfect shuffles!

### How often do you shuffle a deck of cards?

Let’s go nuts and assume that every person who has ever lived shuffled a deck of cards once per second for their entire lives, even in their sleep. That’s 108 billion people times 25,915 days times 86,400 seconds in a day, giving us 241,818,048,000,000,000,000 shuffles. Our new odds: That is, one in 333 quattuordecillion.

**How many shuffles do you need for overhand shuffle?**

The overhand shuffle, by comparison, requires 10,000 shuffles to achieve randomness. “The usual shuffling produces a card order that is far from random,” Diaconis has said.

**Is it true that No 52 cards have ever been shuffled?**

What if I told you that each time you shuffle a deck of cards thoroughly, it is a near certainty that no 52 cards have ever been arranged in that order at any time in history? Hard to believe? It’s true, and it is fairly easy to demonstrate. Let’s start with the number of ways that a deck of cards can be arranged.

#### What are the different types of deck shuffles?

Two popular kinds of shuffles are the random riffle shuffle and the overhand shuffle. The random riffle shuffle is modeled by cutting the deck binomially and dropping cards one-by-one from either half of the deck with probability proportional to the current sizes of the deck halves.