Quick Answer
The U.S. National Academies recommends:
- Men: About 15.5 cups (3.7 liters) per day.
- Women: About 11.5 cups (2.7 liters) per day.
*This includes water from food and other drinks (roughly 20% of intake).
Simple Calculation Method
Body Weight Formula
A personalized way to estimate your baseline need is to drink half your body weight in ounces.
(Your Weight in lbs) ÷ 2 = Daily Ounces
Example: If you weigh 160 lbs, aim for 80 ounces (10 cups) of water daily.
Signs You Are Dehydrated
- • Color Check: Your urine should be pale yellow. Dark yellow or amber means drink more.
- • Fatigue: Even mild dehydration drains your energy.
- • Headache: A common early sign.
- • Dry Skin/Lips: Visible signs your body lacks moisture.
Factors That Increase Need
Sweat & Exercise
Add 12 ounces of water for every 30 minutes of workout.
Heat & Humidity
Hot weather makes you sweat more, requiring increased intake.
Illness
Fever, vomiting, and diarrhea cause rapid fluid loss.
Pregnancy/Breastfeeding
Pregnant women need ~10 cups; breastfeeding women need ~13 cups.
Medical Review
Reviewed by: Ricardo Hamilton, MD
Last Updated: December 15, 2025
Sources: National Academies of Sciences, Mayo Clinic