Shuffled deck
Deck and deal
How many riffles are enough?
| Riffles | Distance from random |
|---|
Total variation distance for a 52-card deck (Bayer and Diaconis, 1992). 1.00 means it is still easy to tell the deck was not shuffled properly, 0 means perfectly random. It only drops sharply after 5 riffles.
This card shuffler mixes a full deck in one tap and lays the whole thing out, top card first. Want four hands of five for a poker night, or 13 each for bridge? Set the numbers and hit Deal. It’s free, works on a phone, and nobody can accuse you of a dodgy overhand shuffle.
How the card shuffler mixes the deck
Every shuffle uses the Fisher-Yates method with your browser’s secure random generator. That sounds technical, but the idea is simple: pick a random card from the 52 for the bottom spot, then a random one from the 51 left for the next, and so on. Each of the 8.07 × 1067 possible orders is equally likely. That number is bigger than the count of atoms on Earth, so the order you’re looking at has almost certainly never existed before.
You can switch to a 54-card deck with two jokers, a 36-card deck (6 up to Ace), a 32-card piquet deck or a 24-card euchre deck. For blackjack practice, set up to eight decks and you get a full shoe.
Dealing hands
Deal hands goes round the table one card at a time, exactly like a dealer would. The cards left over show underneath, faded, so you can use them as the stock in rummy or the community cards in Hold’em. Draw next card is the other way to play: it turns cards over one by one and keeps the last few on screen.
- Texas Hold’em: 2 cards each, up to 10 players
- Five-card draw: 5 each
- Gin rummy: 10 each for two players
- Bridge or whist: 13 each for four
Why seven riffles?
Hand shuffling is a different story. In 1992 the mathematicians Dave Bayer and Persi Diaconis worked out how quickly a riffle shuffle randomises a 52-card deck. After four riffles the deck is still nowhere near random. After five it starts to break up, and at seven it’s close enough that a card player can’t exploit what’s left. The table next to the calculator shows their figures.
Try it: set 3 riffles and press Riffle a new deck. You’ll see long runs of cards still sitting in their factory order, ♠A then ♠2 then ♠3. Do the same with 7 and they’re mostly gone. Most home games shuffle three or four times, which is why the same hands seem to come round again.
Need just one card? The random card generator picks single cards. For the odds of drawing particular cards, use the hypergeometric calculator.
Dealt a bridge hand? Score it with the bridge scorer.