Daily water intake
A weight-based estimate, an adjustment for heat, and the reason your own thirst is a better guide than either.
Total fluid, including what you get from food. Add 0.5–1 litre on hot days.
By body weight
| Body weight | Litres per day | Glasses (250 ml) | Hot weather / heavy sweating |
|---|---|---|---|
| 45 kg | 1.4 – 1.6 L | 5 – 6 | 1.9 – 2.6 L |
| 50 kg | 1.5 – 1.8 L | 6 – 7 | 2.0 – 2.8 L |
| 55 kg | 1.6 – 1.9 L | 7 – 8 | 2.1 – 2.9 L |
| 60 kg | 1.8 – 2.1 L | 7 – 8 | 2.3 – 3.1 L |
| 65 kg | 1.9 – 2.3 L | 8 – 9 | 2.5 – 3.3 L |
| 70 kg | 2.1 – 2.5 L | 8 – 10 | 2.6 – 3.5 L |
| 75 kg | 2.3 – 2.6 L | 9 – 11 | 2.8 – 3.6 L |
| 80 kg | 2.4 – 2.8 L | 10 – 11 | 2.9 – 3.8 L |
| 85 kg | 2.5 – 3.0 L | 10 – 12 | 3.0 – 4.0 L |
| 90 kg | 2.7 – 3.1 L | 11 – 13 | 3.2 – 4.2 L |
| 95 kg | 2.9 – 3.3 L | 11 – 13 | 3.4 – 4.3 L |
| 100 kg | 3.0 – 3.5 L | 12 – 14 | 3.5 – 4.5 L |
| 105 kg | 3.1 – 3.7 L | 13 – 15 | 3.6 – 4.7 L |
| 110 kg | 3.3 – 3.9 L | 13 – 15 | 3.8 – 4.8 L |
This is an estimate of total fluid, and roughly 20–30% of it normally arrives as food — dal, sabzi, curd, fruit, chai. Thirst and urine colour are better day-to-day guides than any formula.
Source: EFSA Panel on Dietetic Products, Nutrition and Allergies. “Scientific Opinion on Dietary Reference Values for water.” EFSA Journal 2010;8(3):1459. The 30–35 ml/kg figure is a standard clinical estimate rather than a national recommendation, and is presented as such.
The honest version
Individual sweat rates differ by a factor of three or more, and a formula based only on body weight cannot know whether you spent the day in an air-conditioned office in Bengaluru or on a Chennai construction site. Use the table as a planning figure and the two real-time signals as the actual guide: thirst, and urine colour — pale straw is right, dark yellow means drink more, and colourless all day usually means you are drinking more than you need.
The Indian summer hydration guide covers heat, humidity and sodium in more detail.
Questions
How much water should I drink a day?
A common clinical estimate is 30–35 ml per kg of body weight of total fluid — about 2.1 to 2.5 litres for a 70 kg adult. Roughly 20–30% of that normally comes from food, so the amount you need to drink is lower than the amount you need to consume.
Is 8 glasses a day correct?
It is a rough approximation with no trial evidence behind it as a threshold. The figure traces to a 1945 recommendation of about 2.5 litres a day which explicitly noted that most of it comes from prepared food — a clause almost always dropped when the advice is repeated.
How much extra water in Indian summer?
Roughly 500 ml to 1 litre more on hot days, and considerably more for outdoor work or training in heat, where sweat losses can exceed a litre an hour. When sweating for hours, plain water alone is not enough — sodium matters too, which is what nimbu-pani with salt, chaas and ORS provide.
Total-water reference values from EFSA (2010); the 30–35 ml/kg estimate is standard clinical practice guidance. General information only — not medical advice. These calculators use published population formulas; they cannot account for your individual health. Consult a doctor before major diet or exercise changes. See data & method for every formula and citation used on this site.