Kidney & hydration
Water Intake Calculator: Your Daily Target
Use this free water intake calculator to find a daily water target based on your weight and how active you are, shown in litres, cups and ounces.
- Free to use
- Works on your phone
- Nothing saved or shared
How to use this calculator
This daily water intake calculator gives you a simple, personal target in a few seconds. Here is all you need to do.
- Choose whether you weigh yourself in kilograms or pounds.
- Enter your weight and pick the activity level that fits a normal week.
- Press Calculate my target to see your daily goal in litres, cups and ounces.
How much water should you drink a day?
If you have ever wondered how much water you should drink, there is no single answer that fits everyone. A common starting point is about 30 to 35 ml of fluid for each kilogram you weigh.
This calculator starts with about 33 ml for every kilogram you weigh, a widely used rule of thumb, then adds a little more for how active you are. Active days and exercise make you lose water through sweat and breathing, so your body needs more to keep up.
Your target is a total from all drinks and watery foods, not water from the tap alone. Hot weather, illness and some health conditions change what is right for you, so treat the number as a friendly guide.
Daily water intake by weight
The chart below shows a rough daily water intake by weight at a light activity level. The calculator above gives your exact figure, but this is handy for a quick look.
| Weight (kg) | Weight (lb) | Daily target (litres) | Cups (8 oz) |
|---|---|---|---|
| 50 | 110 | 1.9 | 8 |
| 60 | 132 | 2.2 | 9 |
| 70 | 154 | 2.6 | 11 |
| 80 | 176 | 2.9 | 12 |
| 90 | 198 | 3.2 | 14 |
| 100 | 220 | 3.5 | 15 |
Why staying hydrated matters
Water keeps your blood flowing easily, helps your kidneys clear waste, cushions your joints, and helps you think clearly. As we get older, the sense of thirst can fade, so it is easy to drink too little without noticing. Keeping a glass or bottle within reach and sipping through the day is one of the simple daily health habits you can keep for your health.
Answers
Frequently asked questions
How much water should I drink a day?
A common guide is about 30 to 35 ml of water for every kilogram you weigh, with more on active or hot days. For many adults that lands near 2 to 3 litres a day from all drinks. This tool gives you a personal starting point based on your weight and activity.
Does tea, coffee and food count?
Yes. Most drinks count toward your fluids, including tea and coffee, and watery foods like soup, fruit and vegetables add more. The number here is a total fluid target, not water from the tap alone.
Can I drink too much water?
It is rare, but drinking very large amounts in a short time can be harmful. If you have heart, kidney or liver problems, or take certain medicines, your doctor may set a specific fluid limit. Always follow their advice over a general calculator.
How do I know if I am drinking enough?
A simple sign is the colour of your urine. Pale straw colour usually means you are well hydrated, while dark yellow suggests you could drink more. Feeling thirsty, tired or lightheaded can also be a nudge to top up.
Does drinking more water help my kidneys?
Staying well hydrated helps your kidneys flush out waste, the same filtering job an <a href="/tools/egfr-calculator">eGFR kidney function calculator</a> helps you measure, and keeps things moving smoothly. That said, people with kidney, heart or liver conditions are sometimes told to limit how much fluid they take in. Always follow your doctor's advice over a general target.
How much water should I drink to lose weight?
There is no magic amount. A glass of water before meals can help you feel full and may support weight loss a little, but water on its own does not melt fat. Aim for your normal daily target and let your food choices and movement do the heavy lifting.
Should I drink more water when it is hot or when I exercise?
Yes. You lose more water through sweat and faster breathing, so add a little extra on hot days and around exercise. Sip steadily rather than gulping a lot at once, and let thirst and the colour of your urine guide how much you top up.