How to play bulls and cows

Your friend writes down a secret number. You guess 1234. “One bull, two cows,” she says, and now you know more than you think. Bulls and cows is the pencil-and-paper game behind Mastermind, and every clue rules something out.

The rules, a first strategy, then bulls and cows apps. Rules vary a little between versions: the length of the number, whether digits can repeat and whether zero can come first. Agree on them before you start, or check the app’s settings.

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Read the clues

A bull means a digit is correct and in the correct position. A cow means the digit is in the number but somewhere else. Zero bulls and zero cows is a great clue too: every digit you guessed is out.

A simple opening

Start with guesses that use completely different digits, like 1234 and then 5678. Between them you learn which digits are in the number before you worry about order. Keep a written grid of what each guess ruled out.

Play against the phone

Apps pick the secret number for you, offer different lengths and add timed or daily modes. Compare them in bulls and cows apps.

More logic games

If you like ruling things out, try number grids; see how to get better at sudoku or how to get better at chess.

Compared from each developer’s own store description.
Step	What you do	Why
1. Secret number	different digits, agreed length	the puzzle
2. Guess	a number of the same length	ask a question
3. Bulls	right digit, right place	locked in
4. Cows	right digit, wrong place	move it around
5. Narrow down	until all bulls	you win

Frequently asked questions

What is the difference between a bull and a cow?

A bull is a right digit in the right place. A cow is a right digit in the wrong place.

Can digits repeat in bulls and cows?

In the classic version, no. Some apps and house rules allow it, so agree first.

Is bulls and cows the same as Mastermind?

Mastermind is a board game based on the same idea, played with coloured pegs instead of digits.