Metabolic Water Calculator
Calculate water produced by oxidizing carbohydrates, fats, and proteins.
Shows why desert animals like camels and kangaroo rats can survive without drinking free water.
When cells oxidize food for energy, hydrogen atoms from food molecules combine with oxygen to form water. This metabolic water is a genuine source of hydration, particularly important for desert-adapted animals.
Water yield from each macronutrient:
Carbohydrates: ~0.60 g water per gram of carbohydrate oxidized. Fats (triglycerides): ~1.07 g water per gram of fat oxidized. Proteins: ~0.42 g water per gram of protein oxidized.
Fat produces the most metabolic water per gram — nearly double that of carbohydrates. This is one reason hibernating and migrating animals rely on fat reserves rather than just energy stores.
The chemistry. For glucose (C6H12O6): C6H12O6 + 6O2 → 6CO2 + 6H2O One mole of glucose (180 g) yields 6 moles of water (108 g), so 0.60 g water per gram of glucose.
For a typical fat like tripalmitin (C51H98O6): C51H98O6 + 72.5 O2 → 51CO2 + 49 H2O One mole (806 g) yields 49 moles of water (882 g), about 1.09 g water per gram of fat.
Real-world examples. A kangaroo rat survives entirely on metabolic water from dry seeds, never drinking free water. A migrating bird crossing the Sahara uses fat stores that produce both energy and water for the journey. Even humans on a 2,000-calorie diet produce roughly 250-350 mL of metabolic water per day.