Which glass contains the most water?
A popular visual riddle asks: “Which glass contains the most water?” You’re shown four identical-looking glasses labeled A, B, C, and D, each filled to about the same visible water level—but each glass also has a different object sitting inside.
At first glance, many people guess the glass that looks the fullest. That’s the trap.
Why the “Fullest-Looking” Glass Isn’t Always the Answer
When you drop an object into water, it displaces some of that water. In other words, the object “takes up space” inside the glass, forcing the water level to rise.
So if the glasses show a similar water level, the one with the largest object actually has less water, because more of the glass’s interior volume is occupied by the object.
Compare the Objects
- Glass A has a large marker.
- Glass B has an eraser (still fairly bulky).
- Glass C has a small paper clip.
- Glass D has a large pocket watch.
Because the paper clip takes up the least space, it displaces the least water—meaning that glass can hold the most actual water while still showing a similar fill level.
The Correct Answer
✅ The glass that contains the most water is: C (the one with the paper clip).
Quick Takeaway
If the water levels appear similar, the glass with the smallest submerged object contains the most water, because less volume is displaced.