How much liquid does an onion produce?

The amount of liquid an onion produces depends on the variety and size of the onion, as well as the method of preparation. On average, a medium-sized onion can produce about 1/4 cup (60 ml) of liquid when chopped or sliced. However, some larger varieties may produce up to 1/2 cup (120 ml) or more. When cooked, onions release even more liquid, as the heat breaks down the cell walls and releases the juices.