Guess Who? Rules and How Many Questions You Need

In Guess Who?, each player secretly holds one Mystery Person among the 24 faces on the board, and players alternate turns asking one yes-or-no question each, flipping down every face that no longer fits. Even a question that splits the faces in half every time needs 5 questions to be certain which person it is, because 24 faces shrink to 12, 6, 3, 2 and then 1. As of October 2026, the rules below follow the Hasbro-hosted rulebook, which carries 1987 and 1996 Milton Bradley copyright dates.

1. What is in the box and how to set up

The game is for 2 players. The box holds 2 gameboards, 48 plastic frames, 48 Face cards, 24 Mystery cards, 8 rubber feet and 2 score keepers. The 48 frames and Face cards fill two boards of 24 faces each. Each player picks a gameboard, flips all of the frames upright, then shuffles the Mystery cards, chooses one at random and slides it into the Mystery card slot facing themselves. The opponent must not see it. The unused Mystery cards go out of play.

2. Turns, questions and guesses

The younger player always goes first. On your turn you do one of two things: ask one question, or guess who the Mystery Person is. Each question must have a "yes" or "no" answer. The rulebook's example is "Does your person have white hair?" After your opponent answers, you flip down every face that no longer fits, and as many as you can. Hair and eye color, rosy cheeks, beards, mustaches, big noses, hats and glasses are the differences the rulebook points to.

You may guess instead of asking. To guess, say something like "The Mystery Person is Paul." Your opponent says whether you are right. If you are right, you win. If you are wrong, you lose the game. The rulebook warns players not to guess until they are ready. The game ends as soon as one player guesses correctly or incorrectly.

3. The Challenge game and championship play

For an extra challenge, both players draw two Mystery cards and place them side by side. The goal is to guess both of the opponent's people, and you must guess both on the same turn. You must say "both" or "either" when asking about them. Asking "Do both of your people wear glasses?" or "Does either of your people have a beard?" is allowed, and "yes" to "either" does not tell you which one, so you cannot flip anything down. For a series of games, the score keeper counts one point per win and the first to win five games is the Champion.

4. How many questions do you need

With 24 faces and one hidden person, the best case for any yes-or-no question is that it splits the remaining faces in half. The count of faces left, in the best case, goes like this:

After 4 questions at best two faces remain, so you cannot be certain of the answer until the fifth question. Four yes-or-no answers can only separate 16 outcomes (2 to the 4th power), and 24 is more than that. Five answers can separate 32, which is enough.

5. What a bad question costs

A question is worth less when it does not split the board evenly. If a question applies to s of the 24 faces, the expected number of faces left after the answer is (s squared plus (24 minus s) squared) divided by 24. The table below uses that formula, assuming the secret face is equally likely to be any of the faces still in play.

Asking about one specific feature that only one face has is about as useful as a guess: you learn almost nothing in the usual "no" case. A question matching 12 faces, such as a feature half the board shares, is the strongest.

6. When a guess is worth making

The odds of a blind guess are the reciprocal of how many faces are left. At the start of the game that is 1 in 24, about 4.2%. With 6 faces left it is about 16.7%, with 3 faces left about 33.3%, and with 2 left 50%. A wrong guess loses on the spot, so a guess at 2 faces is a coin flip for the whole game. Asking one more question can leave a single face, but it also gives your opponent another turn to narrow their own board. The rulebook leaves that trade-off to you.

7. Key takeaways

• 24 faces per board, 24 Mystery cards, and 48 face cards in total.
• One yes-or-no question per turn, or a guess instead. A wrong guess loses.
• The younger player goes first.
• Even perfect halving needs 5 questions to be certain (24, 12, 6, 3, 2, 1).
• In the Challenge game both of the opponent's people must be guessed on the same turn.