Staying properly hydrated supports energy levels, digestion, and overall health. This free online water intake calculator estimates your ideal daily water intake in liters and glasses based on your body weight, daily exercise duration, and climate conditions. Simply enter your details below to get a personalized hydration target.
Estimate how much water you should drink daily based on your body weight, exercise, and climate.
How to Use the Water Intake Calculator
Enter your body weight in kilograms in the "Weight (kg)" field.
Enter how many minutes you exercise per day in the "Exercise Duration (minutes/day)" field (enter 0 if you don't exercise).
Select your climate from the "Climate" dropdown - choose "Normal" or "Hot / Humid".
Click "Calculate Water Intake" to see your recommended daily water intake in liters and glasses.
How the Estimate Is Built
The result adds three parts together:
Base need: body weight (kg) × 0.033 litres, a common rule of thumb of about 33 ml per kg.
Exercise: 0.35 litres for every 30 minutes of exercise, worked out proportionally, so 45 minutes adds 0.525 litres.
Climate: a flat 0.5 litres extra when you choose Hot / Humid.
The total is shown to two decimal places, and the glass count divides it by 250 ml and rounds to the nearest whole glass.
Worked Example
A 70 kg person who walks briskly for 30 minutes a day during a humid Chennai or Mumbai summer: base 70 × 0.033 = 2.31 L, exercise adds 0.35 L and the hot climate adds 0.5 L, for a total of 3.16 litres. Divided by 0.25 L that is 12.64, shown as 13 glasses.
The same person on a cool day without exercise would need about 2.31 L, or 9 glasses. Your target is not fixed; it moves with the weather and your activity.
Estimated Daily Water by Body Weight (No Exercise)
Body weight
Normal climate
Hot / humid
50 kg
1.65 L (7)
2.15 L (9)
60 kg
1.98 L (8)
2.48 L (10)
70 kg
2.31 L (9)
2.81 L (11)
80 kg
2.64 L (11)
3.14 L (13)
90 kg
2.97 L (12)
3.47 L (14)
Figures in brackets are 250 ml glasses. Add about 0.35 L for each 30 minutes of exercise.
Putting the Number in Context
Treat the result as a guide to total fluid, not a quota of plain water. Tea, milk, buttermilk, nimbu pani, coconut water, dal and soups all contribute, and fruit and vegetables add more. Health bodies such as the European Food Safety Authority suggest total water intakes of around 2.0 litres a day for adult women and 2.5 litres for adult men from all drinks and food combined, with more needed in heat and during exercise.
In Indian summers, outdoor workers, travellers and people exercising in the heat can lose well over a litre of sweat an hour. Drinking only water during long, heavy sweating can dilute the body's salt levels, so ORS or a salted drink such as chaas helps replace what is lost. Drink at regular intervals rather than waiting until you are very thirsty.
A simple check is urine colour: pale straw-yellow usually means you are drinking enough, while dark yellow suggests you need more. Some medicines and vitamin supplements can change the colour, so this check is not always reliable.
When This Estimate Does Not Apply
People with kidney disease, heart failure or liver disease are often told to limit fluids. Follow your doctor's limit rather than this calculator.
Pregnant and breastfeeding women usually need more fluid than the formula gives.
Fever, vomiting and diarrhoea raise fluid needs sharply. In these cases, especially for children and older adults, ORS and medical advice matter more than any formula.
Frequently Asked Questions
The calculator starts with a base of about 33 ml of water per kg of body weight, then adds roughly 0.35 liters for every 30 minutes of daily exercise, plus an extra 0.5 liters if you select "Hot / Humid" climate.
Exercise causes you to lose fluids through sweat, so the more minutes you exercise, the more water the calculator adds to your daily total to help you stay hydrated.
Yes. All drinks count, including tea, coffee, milk and buttermilk. The mild diuretic effect of caffeine in normal amounts does not cancel out the fluid in the cup. Food usually supplies around a fifth of total water intake, more if you eat a lot of fruit, vegetables, dal and curries.
It can. Drinking very large amounts in a short time can lower blood sodium to dangerous levels, a condition called hyponatraemia. It is rare in daily life but has been seen in endurance events and drinking challenges. Spread your intake across the day and include some salt or ORS when sweating heavily for hours.
Signs that you are well hydrated include rarely feeling very thirsty and passing pale yellow urine several times a day. Dark urine, headache, dizziness and unusual tiredness can point to dehydration, particularly in hot weather.