Pregnancy Water Intake Calculator
How much water to drink while pregnant or breastfeeding, from body weight, climate and activity — in litres, cups and glasses.
How it works
Fluids ≈ 33 ml × weight + 300 ml (pregnancy) or 700 ml (breastfeeding) + heat and exercise allowances
Blood volume rises by almost half in pregnancy and amniotic fluid is replaced constantly, so needs climb by roughly 300 ml a day; breastfeeding adds about 700 ml because milk is 88% water. The Institute of Medicine suggests about 2.3 L of drinks for pregnant and 3.1 L for lactating women, on top of water in food.
Worked example
68 kg, pregnant, temperate, 30 min exercise: 2,244 + 300 + 350 = 2.9 L — about 12 glasses.
Frequently asked questions
Does tea or coffee count?
Yes, all drinks count, but keep caffeine under 200 mg a day. Water, milk and diluted juice are the best bulk fluids.
Can I drink too much?
Extreme intakes (over 5–6 L) can dilute sodium; otherwise thirst and urine colour are reliable guides.
Related calculators
Educational estimate only — your midwife or doctor will confirm dates and advice for your pregnancy.