Self-working card tricks

The 21 Card Trick

Someone thinks of a card among twenty-one. You deal three times, asking only which pile it is in, and you find it. Deal it through here and watch the possibilities collapse — then learn why their card is always the middle of the last pile, which means you never have to count to eleven.

Out of This World

Someone calls red or black for card after card, face down, and gets every one right. Call them yourself here — then see the thing other explanations skip: one of the two lines always comes out exactly backwards, and that is precisely what makes it fixable.

The Si Stebbins Stack

A deck in a secret order that looks shuffled. Two small sums give you the card under any card named, and where any named card sits. Work it out against the real arithmetic here, then drill it with the sums hidden.

The 27 Card Trick

The bigger, stranger sibling of the 21. Someone thinks of a card and then names any number from 1 to 27, and after three deals their card is sitting at exactly that position.

Why it works: three deals into three piles is counting in base three. Write the position they asked for, minus one, in base 3 and you get three digits; each digit tells you whether to drop their pile on top, in the middle, or underneath that round. Nothing else about it is a decision. Checked: all 27 positions land exactly where requested.

Do As I Do

You and a spectator each take a deck and mirror one another — shuffle, cut, take a card, bury it. Nothing is ever shown or named. Both of you turn over the card you chose and they are the same card.

Why it works: a key card. You glimpse the bottom card of the deck you hand over, and when they cut and complete, your glimpsed card lands directly on top of their selection. Find your key in the deck you get back, take the card beneath it, and that is the card you "chose".

The Four Robbers

Four Jacks break into a house. One goes to each floor of the building — one Jack into each quarter of the deck — the lookout signals, and all four are found together on the roof.

Why it works: three indifferent cards are hidden with the Jacks, and they sit above them, not behind. So the three cards you push into the deck as "Jacks going downstairs" are the strangers, and the real four never move. Get that order backwards and you bury the Jacks instead, which is the one way this fails.

Spectator Cuts to the Aces

The spectator cuts the deck into four piles themselves, moves some cards around under your direction, and turns over the top card of each pile. Four aces. You never touched the deck.

Why it works: the aces start on top and end up in the pile they set down first. Every other pile hands it one card, burying the aces exactly three deep, so moving three cards to the bottom digs them out again, and dealing one onto each pile sends an ace to each. Handled last, it deals itself.

Easy Location

They think of a number, take that many cards, and remember one you never see. Three piles counted down from ten find it. Aldo Colombini's, and the method opens to people who own his book — playing it does not.

Why it works: the number they think of cancels out of the arithmetic completely, which is why you never have to learn it. The rest is Colombini's and sits behind his book. Checked: every number from 1 to 18, over thousands of shuffles.

The 13 Card Trick

You deal the whole deck into piles, counting up to 13 each time. Somebody keeps any three. You gather the rest, look at two of the three, and name the value of the third card, which nobody has seen.

Why it works: two quantities cancel. How many piles you dealt drops out of the arithmetic, and so does every card you dealt into them. Your hand ends up holding 10 plus the three cards still on the table.

Jack the Bounty Hunter

Fifteen cards to them and fifteen to you, and they cut both piles wherever they like. They take a card and decide where it goes. A Jack hunts it down through four rounds of dealing.

Why it works: however the cuts fall, both halves of your fifteen end up between their card and the Jack. That leaves them sixteen apart, and an alternating deal halves the distance each time.

The Piano Trick

Their hands sit on the table like a pianist's. You slot pairs of cards between their fingers, then one last single card. The pairs are split into two piles and, without seeing anything, you name which pile the lone card went to.

Why it works: parity, and nothing else. Splitting pairs keeps both piles even however you do it. One odd card makes exactly one pile odd, and odd or even is the only thing you ever need to know.

The Down Under Deal

They look at the bottom card of a packet of sixteen, then deal it themselves — one card down to the table, one card under, over and over. You never touch it. The card left in their hand is theirs.

Why it works: one pass throws away half the packet and leaves the bottom card on the bottom. Sixteen halves to eight, then four, two, one, so the bottom card survives every pass. Any power of two does the same.

Card Trick with 9 Cards

Nine cards, three piles of three. They keep one pile and remember its bottom card, then spell that card's name themselves — one card dealt for each letter. You are never told what it is, and the fifth card is theirs.

Why it works: dealing a few cards and dropping the rest on top lands a card at ten minus where it started, whatever "a few" was. So a word of unknown length has a known result — and nine is the only packet size it fits.