Water Intake Calculator
Estimate how much water to drink each day based on your body weight and how much you exercise — shown in litres, millilitres, cups and fluid ounces.
How to use it
Enter your weight and your typical daily exercise. The calculator estimates your fluid target using about 35 mL per kilogram of body weight, plus extra for time spent exercising, and converts it into several handy units.
This is a general guide, not a strict rule. You also get water from food and other drinks, and your needs rise in hot weather, at altitude, during illness, and in pregnancy or breastfeeding. Thirst and pale-yellow urine are good everyday signals.
Frequently asked questions
How much water should I drink a day?
A common guideline is about 35 mL per kilogram of body weight, plus roughly 350 mL for every 30 minutes of exercise. For many adults that lands somewhere around 2–3 litres a day from all sources.
Does food count toward water intake?
Yes. Food typically provides around 20% of your fluid intake, and other drinks count too. The figure here is a total target; you don't have to get all of it from plain water.
Can I drink too much water?
Very rarely, drinking extreme amounts in a short time can dilute blood sodium (hyponatraemia). For almost everyone the bigger risk is drinking too little — spread intake through the day rather than all at once.
BriskToolbox provides estimates for general information only and is not medical advice. Talk to a healthcare professional about your individual health.