Everything is worked out in your browser and saved on this device for next time.
About the water intake calculator
How much water do you need? It depends on your body size, how much you move, and the weather. The old rule of "8 glasses a day" is only a rough average. This calculator gives you a number for you.
Type your weight and the minutes of exercise you do on a normal day. Choose the weather where you are. Open More options if you are pregnant or breastfeeding — you need more.
You see your total fluid per day, how many glasses to drink, and how much you can count on getting from food.
How to use it
- Choose kg, cm or lb, ft, in
- Type your weight
- Type the exercise per day (minutes), or press 0, 20, 30, 60 or 90
- Choose the weather where you are
- Read the total fluid, the amount to drink and the glasses
How it is worked out
- About 33 ml per kg of body weight (about 0.5 fl oz per lb) every day
- +12 ml for every minute of exercise (about 350 ml per 30 minutes)
- +500 ml in hot weather, +1,000 ml in very hot or humid weather
- +300 ml if you are pregnant and +700 ml if you are breastfeeding
- About 20% of your fluids come from food (fruit, vegetables, soup), so you drink about 80%
Examples
For 30 minutes of exercise a day and mild weather:
| Weight | Total fluid | In fluid ounces |
|---|---|---|
| 50 kg (110 lb) | 2.0 L | 68 fl oz |
| 60 kg (132 lb) | 2.3 L | 79 fl oz |
| 70 kg (154 lb) | 2.7 L | 90 fl oz |
| 80 kg (176 lb) | 3.0 L | 101 fl oz |
| 90 kg (198 lb) | 3.3 L | 113 fl oz |
| 100 kg (220 lb) | 3.7 L | 124 fl oz |
Water, coffee and tea
Tea, coffee, milk, juice and soup all count, as does water-rich food. Plain water is still the best choice, because it has no sugar and no calories. Alcohol does not count — it makes you lose water.
Signs you need more water
- Dark yellow urine (it should be pale yellow)
- A dry mouth, a headache or feeling tired
- Dizziness when you stand up
- In sport: a fast heartbeat, cramps or a feeling of being too hot
Can you drink too much?
Yes, but it is rare. Drinking several litres in a short time can lower the salt in your blood. Drink steadily through the day, and listen to your thirst.
Tips
- Keep a bottle with you and sip all day
- Drink a glass with every meal and one when you wake up
- Add lemon, mint or fruit if plain water is boring
- In hot weather and when you exercise, drink before you feel thirsty
Frequently asked questions
How much water should I drink a day?
Most healthy adults need about 2 to 3 litres of fluid a day, from drinks and food. The calculator adjusts this to your weight, exercise and the weather.
Is it 8 glasses a day?
Eight glasses of 250 ml is 2 litres — a good rough guide, but not right for everyone. A bigger or more active person needs more.
Does coffee count?
Yes. A normal amount of coffee or tea counts toward your fluids.
How much water when I exercise?
Add about 350 ml per 30 minutes of moderate exercise — the calculator does this. For long or very hot workouts, drink more and add salts.
How much water when I am pregnant or breastfeeding?
About 300 ml more when pregnant and 700 ml more when breastfeeding. Ask your doctor or midwife.
Is this medical advice?
No. It is a general guide. If you have a heart or kidney problem, or a doctor told you to limit fluids, follow your doctor.
Good to know
- Your settings are saved only in this browser
- Nothing you type is sent anywhere
- Units: kilograms and litres, or pounds and fluid ounces — choose at the top
Related tools
- BMI Calculator — your body mass index
- TDEE Calculator — your daily calories
- Macro Calculator — protein, carbs and fat
- Kg to Lbs Converter — convert weights
- Sleep Calculator — rest well too
