HEALTH · WATER INTAKE
Water Intake Calculator
Get your daily water target from the body-weight method and the IOM Adequate Intake, in oz or millilitres.
Daily water target
82.7 oz
2625 mL / 2.63 L
Beverage target3 L / 101.4 oz/day
Total from all sources3.7 L/day
About This Calculator
There is no single "right" amount of water for everyone — needs vary with body size, activity, climate, and health status. This calculator shows two evidence-based targets: the body-weight formula (a practical rule of thumb) and the Institute of Medicine Adequate Intake.
How It Works
Enter your body weight and biological sex (needed for the IOM recommendation, which differs by sex). The calculator returns the body-weight-based target and the IOM beverage target. Switch between oz and mL/L with the unit toggle.
The Formula
oz/day = weight(lb) × 0.5 mL/day = weight(kg) × 35
- weight
- body weight in lb or kg
Frequently Asked Questions
- Why does the IOM recommendation show beverages, not total fluid?
- About 20% of daily fluid intake typically comes from food. The IOM Adequate Intake (3.7 L for men, 2.7 L for women) covers total water from all sources. The beverage portion (~80%) is what you'd actually drink, which is more useful as a daily target.
- Should I drink more when I exercise?
- Yes. Sweat can add hundreds of millilitres per hour of exercise depending on intensity and ambient temperature. A simple rule is to weigh yourself before and after exercise — every kilogram lost equals about 1 litre of fluid to replace.
- Why does biological sex affect the recommendation?
- The IOM Adequate Intake differs by sex because it is based on median observed intake in healthy reference populations, which differ between men and women. The body-weight formula does not require sex.