Water Intake Calculator
Estimate how much water to drink each day from your body weight and activity level.
Enter your details below.
How to use
- Enter your weight in kilograms.
- Choose your activity level for the day.
- Read your daily water target in litres and glasses.
About this tool
This tool starts from a simple rule of thumb — about 35 millilitres of water per kilogram of body weight per day — then adds extra for activity: nothing for light days, half a litre for moderate activity, and a full litre for high activity. It also converts the total into 250 ml glasses. The result is general information only, not medical advice, and hot weather, illness, and diet all change real needs.
Frequently asked questions
Does food count toward water intake?
Yes — food typically supplies around a fifth of daily water, so this target is a guide for total fluids, not a strict drinking quota.
Should I drink more on hot days?
Usually yes; heat and sweating raise losses, so treat this figure as a baseline and drink more when you are sweating heavily.