I have picked a number between 1 and 50!
| Type a number | Enter your guess. |
| Read the clue | Too high or too low narrows the range. |
| New number | Start again with a fresh target. |
Number Guess hides a number and tells you only whether each guess was too high or too low. Narrow it down and find it in as few attempts as possible. It is the simplest guessing game there is, and it happens to be a perfect demonstration of one of computing's most important ideas.
That idea is binary search. If you always guess the middle of the remaining range, you halve the possibilities with every attempt, which means even a range of a thousand numbers falls in about ten guesses. Most people discover this strategy for themselves after a few rounds, which is exactly what makes the game a good teacher.
Always guess the middle of what is left. If you know the number is between one and fifty, guess twenty-five. Whatever the answer, you have eliminated half the possibilities in a single move, which no other guess can match.
Keep track of both bounds, not just the last clue. After a few guesses the range is squeezed from both ends, and players who only remember the most recent hint end up re-testing numbers they already ruled out.
Do not guess at random once the range is small. With four numbers left, the middle guess still beats a hopeful stab, because it guarantees you finish in two more turns rather than possibly four.
Notice how few guesses it actually takes. Halving repeatedly is astonishingly powerful: a range of a thousand needs only about ten guesses, and seeing that for yourself is the real lesson here.
Only whether your guess was higher or lower than the hidden number.
Guess the middle of the remaining range every time. This is called binary search and it is provably the fastest method.
For a range of fifty, about six with good play. Each guess should halve what is left.
Yes. It is the classic hands-on introduction to binary search, a foundational idea in computer science.
Completely free, with no trial and no unlock. Number Guess loads with the page and plays immediately, without an install step or a video ad first.