Daily Water Intake
How much water should you drink a day? The honest answer is that the body that sets nutrition guidelines for the US declines to give a personal formula — and says thirst is a reliable guide for healthy people. What they DO publish is an Adequate Intake for total water by life stage, including a higher figure while breastfeeding. This shows those official numbers, splits out how much is expected to come from drinks rather than food, and — because everyone asks — shows the popular bodyweight rule of thumb clearly labelled as the folklore it is.
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Inputs
- Who is this for?
Man, 19+ / Woman, 19+ / Pregnant / Breastfeeding - Show amounts in
US fl oz / millilitres (mL) - Your weight (optional — see note)
0 - Weight in
pounds (lb) / kilograms (kg)
Frequently asked
What is an 'Adequate Intake'?
A population-level reference figure from the National Academies, based on what adequately-hydrated people were observed to consume. It is not a personal prescription and not a minimum you must hit. Needs rise with activity, heat, illness and pregnancy.
Is the 'half your bodyweight in ounces' rule real?
It is popular, but no health authority publishes it. The National Academies explicitly say they do not offer a rule of thumb for daily glasses of water. We show it because people look for it, labelled honestly — not because it is guidance.
Does coffee or tea count?
Yes. The DRI figures count all beverages, including caffeinated ones, plus the water contained in food — about 20% of the total comes from food.
How much more do I need while breastfeeding?
The Adequate Intake for lactation is 3.8 L/day total water versus 2.7 L for non-lactating women — about 700 mL more, which is roughly the water leaving in the milk.
So how much should I actually drink?
For a healthy adult, the published guidance is to drink to thirst and use the figures here as a sanity check, not a target to force. If you have a medical condition affecting fluid — kidney, heart, or a pregnancy complication — your clinician's number overrides all of this.