About Us
Last updated: 24 October 2026.
Water Intake Calculator is a free tool that estimates how much total fluid you may need each day, based on your weight, age, gender, activity level and climate.
It uses a transparent formula shown on the homepage: weight in kilograms multiplied by 35 ml for adults, plus activity and climate adjustments. The National Academies Adequate Intake values for total water (3.7 litres for men, 2.7 litres for women) are used as a reference point in the guide.
Limits: This is general information only, not medical advice. It does not replace advice from a healthcare professional, especially if you have kidney, heart or liver disease, or a fluid restriction.