Water Intake Calculator
Calculate your recommended daily water intake based on your weight, activity level, and climate.
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How to use this calculator
Base intake plus extra for exercise (500–1000 mL/hr) and hot climate (+500–1000 mL/day).
- 1
Enter your body weight in kilograms.
- 2
Select your daily exercise level.
- 3
Select the climate you live in or work in.
- 4
The result shows your recommended daily water intake in litres, mL, and glasses.
Frequently asked questions
What is the formula behind the daily total?
Your body weight in kilograms is multiplied by 35 to give a base in millilitres. The calculator then adds a fixed amount for the exercise level you pick and another for the climate. Nothing else is considered: age, sex, diet and health are not inputs.
How much does each activity and climate option add?
Activity adds 0 mL (sedentary), 350 (light, 30 minutes a day), 700 (moderate, about an hour) or 1,200 mL (heavy, two or more hours). Climate adds 0 for temperate or cool, 500 for warm or humid, and 1,000 mL for hot or very hot. The choices are fixed amounts, not scaled by body size.
Is the result drinking water only, or all fluid?
The tool does not say and does not split it. It outputs one total of water per day. How much of that you count from tea, soups, fruit or other drinks is up to you, so use it as a rough daily target rather than a bottle count.
How are the glasses and cups worked out?
The total in millilitres is divided by 250 for glasses and by 237 for US cups, and each is rounded to the nearest whole number. A 70 kg sedentary person in a temperate climate gets 2,450 mL, shown as 10 glasses and 10 cups.
What inputs does it reject, and is there an upper limit?
A weight of zero, below zero or a non-number returns an error. There is no upper limit or safety cap, so a very heavy entry in a hot climate with heavy exercise can produce a large figure, such as 5,350 mL for 90 kg. The tool cannot judge whether that suits you.
Who should not follow this number?
Anyone told by a doctor to limit fluids, such as people with heart, kidney or liver conditions, should follow that advice instead. The calculator does not know about medications, pregnancy, breastfeeding or illness. It is general information, not medical advice.
Why is the answer in litres lower than glasses suggest?
Litres are rounded to one decimal and glasses to whole numbers from different divisors, so they can look slightly inconsistent. For example, 5,350 mL shows as 5.3 litres and 21 glasses. The millilitre line is the unrounded figure.
Daily water target — how weight, exercise and climate are combined
A base amount plus two add-ons
The calculation starts with 35 mL for every kilogram you weigh. To that base it adds a fixed allowance for how much you exercise and a second one for the climate you live or work in. The sum is shown in litres, in millilitres, and converted to glasses and cups. Because the add-ons are flat amounts, body weight is the only thing that scales the result, and a small person in a hot climate gets the same extra millilitres as a large one.
The allowances in the code
These are the fixed millilitres added to the weight-based amount.
| Choice | Added per day |
|---|---|
| Sedentary | 0 mL |
| Light exercise (30 min) | 350 mL |
| Moderate exercise (1 hr) | 700 mL |
| Heavy exercise (2+ hrs) | 1,200 mL |
| Temperate / cool | 0 mL |
| Warm / humid | 500 mL |
| Hot / very hot | 1,000 mL |
Worked examples
All figures come from running the calculator. A 70 kg sedentary person in a temperate climate gets 2,450 mL, which is 2.5 litres and 10 glasses. A 60 kg person with moderate exercise in a warm climate has 2,100 mL base plus 700 plus 500, a total of 3,300 mL or 3.3 litres (13 glasses). A 50 kg person with light exercise and a temperate climate gets 2,100 mL. A 90 kg person with heavy exercise in a hot climate gets 3,150 plus 1,200 plus 1,000, which is 5,350 mL.
Using the number day to day
The result is a planning figure, not a measurement of what your body needs on a given day. Thirst, urine colour, illness, and what you eat all shift real requirements. Spreading intake through the day works better than drinking a large amount at once, and the tool’s allowances for exercise and heat only roughly track how much you sweat. If your day is unusually hot or active, expect to need more than the calculator shows.
Limits of a weight-based rule
A per-kilogram rule is a convenient approximation, and several different rules circulate, so it is wise not to treat any single figure as exact. This calculator cannot account for medical conditions, medicines, pregnancy, or doctor-advised fluid limits. People in those situations should follow professional advice. This page is general information and not medical advice.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →