How Much Water Should I Drink a Day?
Healthy US adults get about 3.7 liters (125 oz) of total water a day for men and 2.7 liters (91 oz) for women, including food, according to the US National Academies. About 80% usually comes from drinks. This calculator shows your group's value in liters, ounces and bottles.
How it works
The calculator reads a fixed table of adequate intake (AI) values. The US National Academies of Sciences, Engineering, and Medicine set them in 2005 for total water, which counts drinks plus the water in food. The table also lists the part that usually comes from drinks, about 80% for most groups. The tool converts liters to US fluid ounces (1 liter = 33.814 oz) and divides by your bottle size.
No weight or climate formula is used, because the National Academies do not publish one. If you drink more in hot weather or when you train, add your own estimate in the extra box. This tool gives general reference data and is not medical advice.
Sources
- US National Academies, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005)
- Bottle sizes: Dr. Water product pages
Reference information only. Not medical advice. Last reviewed 2026-10-30.
Frequently asked questions
How much water should an adult drink a day?
The US National Academies set an adequate intake of about 3.7 liters of total water a day for men and 2.7 liters for women aged 19 and older. Total water includes drinks and food. About 80% usually comes from drinks.
Does coffee or food count toward daily water?
Yes. The National Academies value counts water from all drinks and from food. Most people get about 20% of their total water from food.
Is 8 glasses of water a day correct?
Eight 8-oz glasses is 64 oz, about 1.9 liters. That figure is a popular rule of thumb. The National Academies values are higher because they count all water, including food and other drinks.
Do I need more water in hot weather or when I exercise?
Needs usually rise with heat and activity. The National Academies do not give a fixed number for it. Use the extra box to add your own estimate, and ask a health professional for personal advice.
Is this calculator medical advice?
No. It shows published reference values for healthy people. Talk to a health professional if you have a medical condition or take medicine that affects fluid balance.
The HydroTumbler holds 32 oz, so about three fills cover most adult drink targets.
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