There is no universal number
The NHS uses 6–8 cups or glasses of fluid daily as general guidance, noting that heat and prolonged activity can increase needs. This is not an exact measurement in litres: cups vary in size, and food also contributes to your total water intake.
What counts as fluid?
Water is a straightforward choice. Other drinks also contribute to hydration, but their sugars, caffeine and other ingredients still matter. A sweet drink does not become nutritionally equivalent to water simply because it contains fluid. Keep water conveniently available at meals and during breaks in your normal routine.
A practical quantity check
Measure the capacity of your usual glass or bottle once. A 500 ml bottle filled twice contains 1 litre; that is not necessarily your complete daily requirement. This exercise helps you understand quantities, rather than forcing you to drink an inappropriate amount or treating a container count as medical guidance.
When general advice is insufficient
If you have a prescribed fluid restriction, follow your clinical advice. Prolonged sport, illness and specific health conditions need individual consideration. Do not use body weight in an improvised formula to prescribe yourself litres of water, and do not confuse staying hydrated with a method of losing body fat.
