How to understand your result
The calculator begins with body weight and adds broad allowances for the activity and conditions you select. You can optionally add exercise duration, record drinks already consumed and translate the result into your bottle size. It does not measure hydration, replace thirst or account precisely for sweat loss.
A population-level starting point from the NHS, not a personalised prescription.
A transparent planning range that changes with the inputs you choose.
Consider other drinks, moisture in food, exercise, heat and personal medical advice.
What counts towards daily fluid intake?
Plain water is a convenient default, but it is not the only source of fluid. Ordinary tea and coffee, milk, plain sparkling water and diluted drinks can contribute. Food also supplies water, so a total-water reference should not automatically be added on top of every drink you consume.
Use the drink-count checker and beverage audit when you want to separate fluid contribution from caffeine, sugar, alcohol or other considerations.
When your needs may change
Exercise, hot or humid weather, fever, vomiting and diarrhoea can increase fluid losses. Kidney, heart and liver conditions, pregnancy and some medicines can change what is safe. Follow individual clinical advice where it applies, and avoid trying to catch up by rapidly drinking a large volume.
For exercise, measure a representative session with the sweat-rate calculator. For ordinary days, turn the estimate into comfortable servings using the bottle and refill planner.
Daily water intake questions
Short answers to the most common UK calculator questions.
How much water should I drink each day in the UK?
The NHS uses six to eight cups or glasses of fluid a day as a general guide, while needs can increase with activity, heat, illness, pregnancy and breastfeeding. Food and drinks other than plain water can contribute.
Is two litres of water a day enough?
Two litres may suit some days and some people, but it is not a universal target. Body size, exercise, weather, food and other drinks can move an individual estimate in either direction.
Do tea, coffee and sparkling water count?
Ordinary tea, coffee and plain sparkling water normally contribute to fluid intake. Caffeine, sugar, alcohol and dental considerations are separate from whether a drink contains usable fluid.
Can I drink too much water?
Yes. Rapidly drinking very large volumes can dangerously dilute blood sodium. Treat the calculator result as a flexible planning estimate and do not force fluid to complete a target.
Sources and methodology
Free practical resources
Keep the useful numbers close
These resources contain general planning information only. They do not store calculator inputs or include personal health details.
Hydration conversion chart
Litres, millilitres, UK fluid ounces, US fluid ounces, metric cups and common bottle sizes.
Download the CSV chartPrintable daily planner
A simple one-page sheet for planning servings and recording what you actually drink.
Open the printable planner