20 Questions

Overview

One player thinks of something. Everyone else has twenty yes-or-no questions to work out what it is. No equipment, no setup, and it works in a car.

No governing body publishes rules for this game. This page describes the most common form. House rules vary, so agree them before you start.

Play

1. One player — the answerer — thinks of a specific person, place or thing, and does not say it aloud.
2. The other players take turns asking questions that can be answered yes or no.
3. The answerer replies truthfully, with nothing else. No hints, no elaboration.
4. A guess at the answer counts as one of the twenty questions.

Winning

The guessers win if they name it within twenty questions. The answerer wins if they do not.

The traditional opening

The classic first question is whether the subject is animal, vegetable or mineral — a traditional way to split the world into three:

• Animal — any living creature, or something derived from one
• Vegetable — plants and anything made from them
• Mineral — everything inanimate and non-organic

Strictly this is three questions in yes-or-no form, though most tables allow it as one by convention. Agree before you start.

Good and bad questions

The aim is to halve the possibilities with each question. "Is it bigger than a microwave?" splits things broadly. "Is it a kangaroo?" rules out only one thing.

Twenty perfect yes-or-no questions can tell apart just over a million possibilities: 2²⁰ is 1,048,576.

A useful order: category, then size, then whether it is man-made, then location, then function, then specifics.

Variations

• Unlimited questions, counting how many were needed. Lowest count wins over several rounds.
• Everyone but one player knows the answer — the reverse game, where one person must work out what everybody else is thinking of.
• Only the answerer speaks: guessers write questions down, which stops the fastest talker dominating.

Choosing a good subject

Something specific enough to be a real answer, but well-known enough to be guessable. "A pelican" is good. "My neighbour's car" is not — there is no line of questioning that reaches it.

Hints and wrong guesses

The answerer may not give hints. Replies are yes or no only. "Sort of" or "getting warmer" breaks the game — the constraint is the entire point.

Two exceptions are commonly agreed in advance: "irrelevant" for a question that does not apply, and "I don't know" where the answerer genuinely cannot say.

Wrong guesses count as questions. Naming a specific answer uses one of your twenty. There is no separate allowance, and no limit on how many of the twenty you spend guessing rather than narrowing.

Commonly argued

• Yes or no only. No warmer, no colder, no hints.
• A wrong guess costs a question.
• Animal, vegetable or mineral is three questions strictly, though nearly everyone allows it as one.