Water intake varies with weight because the body’s hydration needs depend on overall mass and metabolic activity. Heavier individuals require more water to support essential functions like circulation, digestion, and temperature regulation, as their bodies have a greater volume of tissues and fluids. In contrast, lighter individuals need less water since their metabolic demands are lower. A general guideline suggests consuming 35–40 mL of water per kg of body weight to maintain proper hydration. Additionally, factors such as physical activity, climate, and diet also influence daily water requirements, making hydration needs unique for each person