Water for a 100 kg person
A planning estimate, not a requirement — thirst and urine colour remain the better day-to-day guide.
3.0 – 3.5 L A 100 kg adult needs approximately 3.0 to 3.5 litres of total fluid a day, using the standard clinical estimate of 30–35 ml per kg. That is about 12 to 14 glasses of 250 ml.
Roughly 20–30% of total fluid arrives as food — dal, sabzi, curd, fruit and chai all count — so the amount you need to drink is meaningfully less than the figure above. On a hot day, add 0.5–1 litre.
Every 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.
What moves this number
- Heat and humidity. Sweat that cannot evaporate does not cool you, so a humid 35 °C day costs more fluid than a dry 40 °C one.
- Physical work. Sustained outdoor labour or hard training can exceed a litre of sweat an hour.
- What you eat. A diet heavy in dal, sabzi, curd and fruit supplies far more water than one built on dry snacks.
- Illness. Fever, vomiting and diarrhoea raise requirements sharply and change the advice entirely — that is an ORS situation, not a calculator one.
Source: EFSA Panel on Dietetic Products, Nutrition and Allergies. “Scientific Opinion on Dietary Reference Values for water.” EFSA Journal 2010;8(3):1459.
Questions
How much water should a 100 kg person drink?
About 3.0 to 3.5 litres of total fluid a day at 30–35 ml per kg, which is roughly 12–14 glasses of 250 ml. Around 20–30% of total fluid normally comes from food, so the amount to actually drink is lower.
How much water in hot weather at 100 kg?
Add roughly 500 ml to 1 litre on a hot day — so 3.5 to 4.5 litres — and more again for outdoor work or training in heat, where sweat losses can exceed a litre an hour.
Total-water reference values from EFSA (2010); 30–35 ml/kg is a standard clinical estimate. 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.