Daily Water Intake Calculator

What this tool does

It gives a general daily fluid range for a healthy adult from body weight and daily exercise. Fluid means drinks of any kind, not only plain water. The result is a range, not a single target, because needs vary several-fold between people.

Method used

Baseline: 25 to 35 ml of fluid per kg of body weight a day, the range given in the BDA Manual of Dietetic Practice ("In health, fluid requirements are 25-35 mL/kg body weight"). Exercise: 0.4 to 0.8 L per hour, the starting point in the American College of Sports Medicine position stand on exercise and fluid replacement (Sawka et al., 2007), which also warns against drinking more than you sweat. No fixed hot-weather allowance is added: sweat losses in heat range from about 0.5 to 2 L an hour, far too wide for a single number. Weighing yourself before and after exercise shows your own loss.

Fluid, water and food

Reference values for total water intake, such as the European Food Safety Authority's 2.0 L a day for women and 2.5 L for men, include the roughly 20% of water that usually comes from food, so they are not directly comparable with this fluid estimate.

Frequently asked questions

Does this include water from food?
No. It estimates fluid from drinks. Food typically adds about a fifth of total water intake on top.

Is this medical advice?
No. It is a general guideline for healthy adults. People with kidney, heart or liver conditions, or who have been told to limit fluids, should follow their doctor's advice instead.