Daily Water Intake
Calculator
Find your personalized daily hydration goal based on weight, activity level, and climate.
π‘ Includes fluid from all sources. Adjust for illness or medical conditions. Consult your doctor for clinical advice.
Frequently Asked Questions
How much water should I drink per day?
The US National Academies of Sciences recommends about 125 oz (3.7 L) total daily fluid for men and 91 oz (2.7 L) for women β including water from food (~20%). Your personal need varies by body weight, activity, climate, and health status. Our calculator personalizes this estimate for you.
Is the "8 glasses a day" rule accurate?
The 8x8 rule (eight 8 oz glasses = 64 oz/day) is a rough starting point but not scientifically precise. It doesn't account for body size, activity, or climate. A 250 lb athlete training in heat needs far more than a 130 lb sedentary person in an air-conditioned office. Weight-based formulas like ours give a better estimate.
Does coffee or tea count toward daily water intake?
Yes β despite the common myth, caffeinated drinks like coffee and tea do count toward hydration. The mild diuretic effect of caffeine is more than offset by the water content of the beverage. Alcohol has a stronger diuretic effect and should not be counted. Plain water, herbal tea, milk, and juice all count toward total fluid intake.
How do I know if I'm drinking enough water?
The simplest check is urine color. Pale yellow means well hydrated. Dark yellow or amber means drink more. Clear urine may indicate overhydration. Other signs of dehydration include thirst, dry mouth, fatigue, dizziness, and headaches. Note that B vitamins can make urine bright yellow regardless of hydration status.
Why do I need more water in hot weather or at altitude?
In hot or humid climates you lose more water through sweat. At high altitude (above ~8,000 ft), your breathing rate increases to compensate for lower oxygen, and you lose more water vapor through respiration. Both situations significantly increase fluid needs β by 12β25% or more depending on conditions.
Do pregnant or breastfeeding women need more water?
Yes. Pregnant women need about 10 extra oz (300 mL) per day for amniotic fluid and increased blood volume. Breastfeeding women need significantly more β roughly 25 extra oz (700 mL) per day β because breast milk is about 88% water. Our calculator adds these amounts automatically when you select the relevant option.