It is commonly said to drink eight glasses of water each day but this is sometimes too much or too little for your body’s hydration needs. I could do a bunch of different calculations to find out your fluid needs but it varies depending on your age, activity levels, sweat, health, digestion, diet and stage of life (pregnant, breast-feeding, elderly, etc.).
Source: How Much Water Should I be Drinking? | Food & Nutrition | Stone Soup