What is a water intake calculator?
A water intake calculator estimates how much water you should drink every day. The old "8 glasses a day" rule ignores the fact that a 50 kg student and a 95 kg construction worker in the summer heat need very different amounts. This free online water intake calculator starts from your body weight in kg, then adds water for exercise, hot weather, pregnancy, breastfeeding or creatine use, and shows the result in litres, 250 ml glasses and ounces.
How much water should I drink a day?
Most healthy adults need about 30–35 ml of water per kg of body weight per day as drinking water. For a 70 kg adult that is roughly 2.1–2.5 litres. Official reference values give total water from all drinks and food:
| Source | Men | Women |
|---|---|---|
| US National Academies (total water, food + drinks) | 3.7 L/day | 2.7 L/day |
| European Food Safety Authority (total water) | 2.5 L/day | 2.0 L/day |
| Typical share from drinks (about 80%) | 2.0–3.0 L | 1.6–2.2 L |
About 20% of your water comes from food – fruit, vegetables, dal, curd and rice all contain water – so the calculator's result is your target for drinks.
How to calculate water intake by body weight
This daily water intake formula is used by the calculator:
Water (ml) = weight (kg) × 35 + 350 ml per 30 min of exercise + climate + special needs
- Weight × 35 ml – the base need for a healthy adult.
- Exercise – about 350 ml for every 30 minutes of activity to replace sweat.
- Climate – +500 ml in hot or humid weather such as an Indian summer, −250 ml if you spend the day in cool air-conditioning.
- Pregnancy +300 ml, breastfeeding +700 ml, creatine +500 ml.
Worked example
A 70 kg person who exercises for 30 minutes a day in a hot climate needs 70 × 35 = 2,450 ml, plus 350 ml for exercise and 500 ml for heat = 3,300 ml, or about 3.3 litres. That is roughly 13 glasses of 250 ml or 112 US fluid ounces. The same person in a cool office with no exercise needs about 2.2 litres.
Water intake calculator for weight loss
Water does not burn fat by itself, but it helps weight loss in practical ways. Drinking 500 ml of water before meals has been shown to reduce how much people eat, and replacing sugary drinks, packaged juice and sweetened chai with water can remove hundreds of calories a day. Staying hydrated also supports exercise performance and makes a higher-protein diet easier on the body. Pair your water target with a calorie goal from the calorie calculator and track activity with the calories burned calculator.
Water intake during pregnancy and breastfeeding
During pregnancy, blood volume and amniotic fluid increase, so fluid needs rise by about 300 ml a day. Breastfeeding mothers lose around 700 ml a day in breast milk and need to replace it. A practical tip is to drink a glass of water every time you feed the baby.
Water intake calculator for creatine users
Creatine pulls water into muscle cells. Most people taking 3–5 g of creatine a day do well by adding about 500 ml to their usual intake, especially on training days. There is no need for extreme amounts.
Water intake for kids and the elderly
Children need less in absolute terms but more per kg. Rough guides: 1–3 years about 1.0–1.3 litres total water, 4–8 years about 1.2–1.7 litres, 9–13 years about 1.6–2.4 litres. Older adults often feel less thirsty, so they should drink on a schedule rather than wait for thirst.
Signs you are drinking enough
- Pale straw-coloured urine through the day.
- Urinating every 3–4 hours.
- Rarely feeling thirsty, with no headaches or dizziness in the heat.
Dark yellow urine, dry mouth, fatigue and headaches suggest you need more. It is also possible to drink too much: more than about 1 litre an hour for several hours can dilute blood sodium (hyponatremia), which is dangerous, so spread your water across the day.
Tips to reach your daily water goal
- Keep a 1-litre bottle at your desk and refill it two or three times.
- Drink a glass on waking and one with every meal.
- Coconut water, buttermilk (chaas), lemon water and herbal tea all count; so do tea and coffee in moderate amounts.
- Use a water intake tracker app or phone reminders if you forget.
- Drink 400–600 ml in the two hours before exercise and sip during long sessions.
Weight, age, pregnancy and exercise: what to enter
Water intake calculator by weight
Your weight in kg is the main input: the water intake calculator works according to weight, starting from 35 ml per kg, then adds for activity, heat and other factors.
Water intake calculator in litres, ml and oz
Results show in litres, in ml per hour and in oz, so they also answer "how many ounces of water should I drink".
Water intake calculator for men, women and kids
Men and women use the same method. For kids or a toddler, use the age guide above. Elderly people should set reminders, because thirst fades with age.
Water intake calculator by age
Age matters most for children and older adults. For adults 18–65, weight and activity matter more than age.
Taking creatine
Choose "Taking creatine" and the tool adds 500 ml to your normal need. That is how to calculate water intake for creatine.
Water intake calculator pregnancy
Choose "Pregnant" for a result during pregnancy, and "Breastfeeding" after the baby is born.
Exercise
Add your minutes of activity and the extra water for exercise is included. It also supports muscle growth, since muscles are about 75% water.
Height and weight
A water intake calculator based on height and weight is not needed: weight already reflects body size, and height adds little once weight is known.
What is normal water intake per day?
The normal water intake per day for adults is about 2–3 litres of drinks. The minimum water intake per day to avoid dehydration is roughly 1.5 litres for a sedentary adult in a cool climate. That is the recommended water intake per day in most guidelines, and the daily goal a water intake calculator gives most adults in India and worldwide.
To calculate water intake per day or calculate water intake by weight by hand, multiply kg by 35. That is how to calculate water intake by body weight and how to calculate water intake based on weight in kg. If you want to lose weight, the free water intake calculator uses the same number – see the weight loss section.
Is this water intake calculator online free to use?
Yes. The calculator needs no sign-up, and it answers what should my water intake be and how much water you should drink per day, with a daily target in litres.
Water intake calculator for weight loss (female example)
While losing weight, base the water intake calculator on your current weight, not your goal weight. A 65 kg woman who walks 30 minutes a day needs about 65 × 35 + 350 = 2,625 ml, or roughly 2.6 litres, from all drinks. Food supplies extra water on top, especially fruit, vegetables, dal and curd. A glass before each meal is an easy way to spread it out.
Water intake calculator for Malaysia, Singapore and NZ
The formula is the same in every country; only the climate setting changes. In hot and humid Malaysia and Singapore, choose the hot climate option to add about 500 ml. In New Zealand's cooler months, the normal setting is usually right; add the hot setting in summer or when you work outdoors. The results are in litres and ml (metric), with US ounces shown for reference.
Water consumption calculator India: household use
Drinking water is only a small part of household water. Indian planning norms (CPHEEO) use about 135 litres per person per day for urban homes with sewerage, covering bathing, flushing, washing and cooking. A family of four therefore uses about 540 litres a day, or roughly 16,200 litres a month. Drinking water is only about 2–4 litres per person of that.
Water intake calculator for dogs
A healthy dog drinks roughly 50–60 ml per kg of body weight a day, so a 20 kg dog needs about 1–1.2 litres. Dogs need more in hot weather, after exercise and on dry food. A sudden large rise in thirst can be a sign of illness, so mention it to your vet.
Water intake calculator app
You do not need to install a water intake calculator app; this page is free and works in any phone browser. To track the target, a free reminder app or simply a marked 1-litre bottle filled two or three times a day works just as well.
Frequently asked questions
How much water should I drink per day?
A good estimate is 35 ml per kg of body weight, plus about 350 ml per 30 minutes of exercise and 500 ml extra in hot weather. For a 70 kg adult that is 2.5–3.3 litres.
How do I calculate water intake by weight in kg?
Multiply your weight in kg by 35 to get millilitres. For example, 60 kg × 35 = 2,100 ml, or 2.1 litres a day.
How many glasses of water should I drink a day?
Divide your daily target in ml by 250. A 2.5 litre target is 10 glasses of 250 ml.
How much water should I drink in a day in India?
Because of the heat and humidity in much of India, most adults need 2.5–3.5 litres a day, more if they work outdoors or exercise.
Does tea or coffee count towards water intake?
Yes. Moderate amounts of tea and coffee hydrate you almost as well as water. Alcohol and very sugary drinks are not good substitutes.
How much water should I drink on creatine?
Add about 500 ml to your normal daily water intake while taking creatine.
Can I drink too much water?
Yes. Drinking several litres in a short time can cause low blood sodium. Spread your intake across the day and let thirst and urine colour guide you.
How much water should I drink while losing weight?
Use your current weight: about 35 ml per kg, plus about 350 ml for every 30 minutes of exercise. A 65 kg woman who walks for 30 minutes needs roughly 2.6 litres.
How much water does a dog need a day?
Roughly 50–60 ml per kg of body weight, so about 1–1.2 litres for a 20 kg dog, more in hot weather or after exercise.
Last updated 2026-09-18