Most adults are made of roughly 50–60% water by body weight , which for a 70 kg person works out to about 35–42 liters of water in total.

Quick Scoop

  • Adults: usually about 60% water on average.
  • Adult men: often around 60% (≈42 liters for 70 kg).
  • Adult women: often around 50–55% (≈31–35 liters for 70 kg).
  • Range overall: about 45–75% water depending on age, sex, and body fat; infants are highest, older adults and people with higher body fat are lower.
  • Babies: can be around 70–78% water at birth , then the percentage slowly drops toward adult levels.

Mini breakdown: where that water is

Water is spread throughout all your tissues, not just “sloshing around” as one big pool.

  • Inside cells (intracellular fluid): about two‑thirds of your total body water.
  • Outside cells (extracellular): about one‑third , including fluid between cells and blood plasma.

Some organs are especially watery:

  • Brain and heart: roughly 73–80% water.
  • Lungs: about 75–83%.
  • Muscles and kidneys: around 75–80%.
  • Skin: around 64–75%.
  • Bones: only about 20–30%.

As a simple picture: a 70 kg adult man typically carries about 42 liters (≈11 gallons) of water , while a 70 kg woman carries about 31–35 liters (≈8–9 gallons).