How to Calculate Your Daily Water Intake
Follow the site’s broad weight-based heuristic, convert units, and understand why the result is not a personal prescription.
1. Choose a method and its scope
The site’s adult weight tool uses 30–40 mL/kg/day as a rough heuristic. It is not a clinically validated formula or universal recommendation. Official Adequate Intakes use a different population-reference method and include water from food and beverages.
2. Convert body weight to kilograms
If your weight is in pounds, divide by about 2.20462 (or multiply by 0.45359237) to get kilograms. For example, 154 lb is about 69.9 kg. The Water Intake Calculator by Weight converts pounds automatically.
3. Apply the heuristic and convert units
For 70 kg, multiplying by 30 and 40 mL gives 2,100–2,800 mL, or 2.1–2.8 L. Multiply liters by about 33.814 to convert to US fluid ounces. These conversions do not make the estimate more precise.
4. Interpret the range
Food and other beverages contribute water. Weight alone does not account for age, activity, temperature, pregnancy or breastfeeding, illness, medicines, or medical conditions. Follow individualized care advice or fluid limits.
Common questions
Should I choose 30 or 40 mL/kg?
The site shows a broad range rather than selecting one clinical target.
Does the calculation include food water?
It does not measure food moisture; treat it as a rough heuristic.
Who should not rely on this tool?
It is not designed for children or people who need individualized medical fluid guidance.
Sources and further reading
Sources support the specific guidance described above. This page is general information, not diagnosis or individualized medical advice.