To keep functioning normally, your body needs a steady supply of water. You lose water through sweat, breathing and going to the toilet. So exercise, playing sports, hot weather, vomiting (being sick) or having diarrhoea (runny poo) can change how much water you need.
Did you know it's not just water that counts?
Water (fluid) comes from what you drink and many everyday foods. We get about 20% of our water intake from food. Foods like watermelon and lettuce contain lots of water. So, it's really fluid that we're talking about, not just water.
As a rough guide, adults should aim for 1.5–2 litres (6–8 cups) of fluid each day and children 1–1.5 litres (4–6 cups). This includes most drinks, eg, water, milk, tea or coffee – but don't count alcohol in this total as it dehydrates you.
If you're losing more fluid because of hot weather, sweating, playing sports, vomiting or having diarrhoea, you'll need to drink more.
If you're having to pee 4–5 times a day, and your pee is a pale yellow colour, you're probably getting enough fluid. If it is dark yellow you are not drinking enough, and if it looks like water you are drinking too much.