About Water Jugs
Water jug puzzles are some of the oldest measuring puzzles there are: jugs of awkward sizes, no markings on them, and an exact amount to measure. Sharing puzzles like the 8, 5 and 3 litre one go back at least four hundred years, and a version with 3 and 5 gallon jugs turned up in a 1990s action film. Water Jugs gathers seven, from that classic four litres to sharing a barrel into equal halves with no tap at all. Each one has been solved by a program, so the page knows the fewest moves it takes.
How to play Water Jugs
- Each puzzle gives you jugs of different sizes and an amount to measure. The jugs have no markings: a jug is full, empty, or holds what you poured into it.
- Tap a jug to pour from it, then tap the jug to pour into. Pouring stops when the first jug is empty or the second is full.
- When there is a tap, Fill and Empty under each jug fill it to the top or pour it away. Without a tap, you can only pour between the jugs.
- Reach the goal shown above the jugs. The fewest moves earn three stars. Your progress is saved on this device only.
Tips & strategy
- With two jugs and a tap, keep to one rhythm: fill the same jug, pour it into the other, and empty the other whenever it is full.
- Look at what is left over. Pouring a full 5 litre jug into a 3 litre jug leaves 2, and that 2 is often the step that matters.
- Without a tap the total never changes, so picture where each part of the water has to end up.
- If one way round takes too long, try the other: starting with the bigger jug or the smaller one can change the count a lot.
Water Jugs: questions and answers
Can every water jug puzzle be solved?
Not every one. With two jugs and a tap you can only measure multiples of the largest number that divides both sizes: with 4 and 6 litre jugs, only even amounts. Every puzzle here can be solved.
What counts as a move?
Filling a jug, emptying it or pouring from one jug into another. A move that would change nothing, like filling a full jug, is not allowed and is not counted.
Is my progress saved?
Yes, in your browser on this device: the puzzles you have solved, your stars and your best result for each. Water Jugs runs entirely on your phone or computer.