How much water should I drink a day?

Bottom lineMost women need about 2.2 liters of fluids a day (8-9 glasses), scaled by body weight at 30-35 ml/kg, plus 350-1,000 ml for exercise, ~500 ml in hot climates, ~300 ml in pregnancy, and ~700 ml while breastfeeding; all drinks except alcohol count, and pale-yellow urine is the practical check.

For most women, about 2.2 liters of fluids a day - roughly 8-9 glasses. That comes from the Institute of Medicine's adequate intake of ~2.7 liters of total water for women, of which about 80% comes from drinks and 20% from food.

What changes your number

• Body size: the working rule is 30-35 ml per kg of body weight
• Exercise: add 350-1,000 ml depending on duration and intensity
• Hot or humid climate: add ~500 ml
• Pregnancy: add ~300 ml - blood volume expands by up to 50%
• Breastfeeding: add ~700 ml - milk is almost 90% water (a glass every nursing session is the easy habit)

What counts

Everything except alcohol: water, tea, coffee (normal caffeine intakes are only mildly diuretic and still hydrate), milk, soups. You don't need to hit the target with plain water alone.

Your cycle and water

Premenstrual bloating is hormone-driven fluid retention - and restricting water makes it worse, because your body responds to scarcity by holding on. Steady intake, less salt, and light movement is the combination that actually helps. Mild dehydration also measurably worsens period cramps and headaches, so the days around your period are the worst time to run dry.

The simple check

Pale-yellow urine means you're hydrated; dark yellow means drink more. Thirst, afternoon headaches, and unexplained fatigue are the common early flags.

Calculate yours: water intake calculator · how to reduce period bloating