How much water do you actually need?
A common baseline is about 35ml of water per kilogram of body weight per day. For a 65kg adult, that's roughly 2.3 litres before accounting for exercise or climate. This calculator adds extra for activity level and hot or humid conditions, since sweat losses increase your fluid needs.
Signs you're not drinking enough
Thirst, dark yellow urine, fatigue, and headaches are common early signs of mild dehydration. Urine that's pale straw-colored is generally a good sign you're well hydrated.
Does all fluid count?
Water is best, but tea, milk, and water-rich foods (fruits, vegetables, soups) also contribute to daily hydration. Caffeinated and sugary drinks can count too, though in moderation — they're not a full substitute for plain water.
Frequently asked questions
Is 8 glasses a day accurate for everyone? It's a reasonable general guideline, but actual needs vary by body size, activity, and climate — this calculator gives a more personalized estimate.
Can you drink too much water? Yes, in rare cases (overhydration/hyponatremia), especially during intense endurance exercise. For general daily use, the amounts here are a safe target range.