Potatoes are roughly 80% water.

The common potato, known scientifically as Solanum tuberosum, typically consists of 78% to 80% water and 20% solids. These solids are primarily composed of starch, which makes up about 85% of the dry mass. The high water content is stored within the vacuoles of the plant's parenchyma cells.The structural integrity of a raw potato comes from turgor pressure. This is the force of the water pushing against the rigid cellulose cell walls. When this pressure is high, the potato feels firm and crisp to the touch. If the potato loses water through evaporation, it becomes soft and shriveled.During the cooking process, heat causes the cell walls to break down and the starch granules to gelatinize. As the internal temperature rises, the water inside the cells turns into steam and escapes. Research from food science institutions shows that a potato can lose up to 20% of its total weight during baking due to this moisture loss.This high water-to-starch ratio is why potatoes are classified into different culinary categories. Waxy potatoes have slightly more water and less starch, allowing them to hold their shape better. In contrast, starchy potatoes like the Russet have slightly less water, resulting in a fluffy texture when the internal moisture evaporates during cooking.