Pregnancy · Hydration

Pregnancy Water Intake Calculator

A personalised daily water target combining your body weight, activity level and climate with the Institute of Medicine's pregnancy Adequate Intake. Output in litres, fluid ounces and 8-ounce cups.

Last reviewed 22 May 2026

Daily water intake

How much water do I need in pregnancy?

Activity level

Enter your pre-pregnancy weight to see your daily water target.

How to use this calculator

Enter your pre-pregnancy weight, your usual activity level, and tick the hot-climate box if you live somewhere warm or are travelling in the heat. The calculator returns a daily target rounded to the nearest 100 mL.

Background — pregnancy and fluid needs

Pregnancy expands plasma volume by roughly 45 % above pre-pregnancy baseline. Amniotic fluid alone reaches ~800 mL by mid-pregnancy. Renal blood flow rises and the kidneys filter more, raising the baseline water turnover.

The Institute of Medicine’s Adequate Intake (AI) for pregnant women is 3.0 L of total water per day (≈ 12.7 cups), with about 2.3 L expected from beverages and the rest from food. That is about 300 mL above the non-pregnant AI of 2.7 L.

Layer evidence-based adjustments on top:

  • Activity: add ~400 mL for moderate exercise, ~800 mL for heavy exercise.
  • Climate: add ~500 mL in heat or low humidity.
  • Body mass: larger bodies have larger water turnover.

Interpreting your result

The target is a daily guide — spread your intake across the day in 200–250 mL servings every 1–2 hours rather than chasing a number in big bursts. Urine colour is the simplest check: pale straw means hydrated, dark yellow means drink more.

Limitations

  • Pre-eclampsia, kidney disease, and some cardiac conditions affect fluid balance and require physician-set targets.
  • Hyperemesis gravidarum disrupts intake; IV fluids and prescription antiemetics may be needed.
  • Twin / multiple pregnancies have larger plasma expansion and slightly higher needs.
  • Drinking more than ~1 L per hour can dilute serum sodium (hyponatremia). Spread intake out.

Sources

  • Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press, 2005.
  • Larson-Meyer DE. Vegetarian and vegan diets for athletic training and performance. Sports Sci Exch 2010;23(106). (Activity-water relationship.)
  • American College of Obstetricians and Gynecologists. Nutrition during pregnancy (FAQ).
  • Mulyani EY, et al. Effect of dehydration during pregnancy on birth weight and length. J Pregnancy 2021.

Frequently asked questions

How much water should I drink during pregnancy?
About 2.3–3.0 litres of beverages per day for most pregnant adults — roughly 8–12 eight-ounce cups. The Institute of Medicine's Adequate Intake (AI) for pregnant women is 3.0 L of total water per day, of which ~2.3 L comes from beverages and the rest from food.
Why do I need more water in pregnancy?
Pregnancy expands maternal blood volume by ~45 %, supports amniotic-fluid production, and increases kidney filtration. Mild dehydration drops blood pressure and can trigger Braxton-Hicks contractions, dizziness, headaches and constipation — all easier to prevent than to treat.
What counts as water?
Plain water, milk, herbal tea (within pregnancy-safe limits), broth, and high-water foods (cucumber, watermelon, soups, citrus) all count toward total water. Coffee and tea also contribute despite the caffeine's mild diuretic effect — though stay within ~200 mg caffeine/day in pregnancy.
Can you drink too much water in pregnancy?
Yes, though it takes effort. Drinking more than ~1 L per hour can dilute sodium and cause hyponatremia (low blood sodium), which is dangerous. Spread your intake across the day rather than chugging large amounts at once. If you're producing very pale, very frequent urine and feel sluggish, you may be over-doing it.
How do I know if I'm well hydrated?
The simplest check is urine colour: pale straw is well-hydrated; dark yellow means drink more. Pregnant people typically urinate every 1–2 hours when adequately hydrated. Persistent thirst, dry lips, dizziness on standing, headache and reduced urine output are signs of dehydration.

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