Where the numbers come from.

Is water intake calculated by weight?

Body size matters, but weight alone cannot establish an individual daily requirement. This tool uses a published reference rather than assigning a fixed number of milliliters per kilogram.

The source of the displayed amounts

The calculator uses the adult table in the U.S. National Academies’ 2005 Dietary Reference Intakes report, Summary Table S-2. It distinguishes beverages from food and total water. These are population references, not a minimum or a prescription for each person.

What newer research adds

Yamada and colleagues, Science (2022), studied water turnover in 5,604 people across 26 countries. Age, body size, activity and environment were associated with turnover. Their adult prediction equation explained 47.1% of its variation. However, turnover includes more than drinks, and the study did not assess whether participants were adequately hydrated. We do not convert that equation into a personal drinking target.

Seal and colleagues, European Journal of Nutrition (2023; online 2022), studied 99 healthy U.S. adults. Their findings support the National Academies’ total-water references against a urine-concentration criterion. They measured 24-hour urine on one day and excluded people exercising more than four hours a week. This supports a general starting point, not a sports prescription. The study was funded by Danone Research and included authors with declared industry relationships.

What your profile changes

Your age range determines whether this adult reference applies and adds context for older adults. Your type of day brings up guidance for exercise or heat. These answers do not change the published volume. We do not ask for weight because we do not use a weight-based equation.

What we calculate

In reference mode, beverage volume divided by container capacity gives the container count. In conversion mode, we divide the volume you enter by container capacity; that amount is your input, not our recommendation. US fluid ounces are converted using 29.5735295625 ml per US fl oz; bottle counts are rounded to two decimal places. The bottle drawing is illustrative, not a calibrated liquid gauge.

Scope and limits

This version displays adult references for ages 19 and over. It does not provide personalized advice for pregnancy, breastfeeding, medical conditions or prescribed fluid restrictions. It does not estimate sweat losses, diagnose dehydration or recommend an hourly drinking rate.

The food portion is from the reference table, not an estimate of your own meals. Intakes below an adequate-intake reference do not automatically mean dehydration. Activity and environment can change needs.

Evidence and responsibility

This is an independent educational tool, not a clinical service. References were checked on September 7, 2026. The calculator has not been clinically validated or reviewed as an individual prescription.

Project and editorial responsibility: Jorge Isaac Avilés Monroy, site owner. This identifies who maintains the site; it does not indicate medical authorship or clinical review. About this project.