7 min read
2026-02-01
The popular “8 glasses a day” rule is an oversimplification. The actual need depends on weight, activity, climate and diet.
**30-35 ml per 1 kg of body weight**
Example: a person weighing 70 kg - 2100-2450 ml per day.
Every 30 minutes of training: +350-500 ml
Heavy physical labor: +500-1000 ml
Hot weather (over 30°C): +500-1000 ml
Dry air (heating in winter): +300-500 ml
| Factor | Additional |
|---|---|
| Physical activity | +350-500 ml / 30 min |
| Heat (over 30°C) | +500-1000 ml |
| Pregnancy | +300 ml |
| Breastfeeding | +500-700 ml |
| Illness with fever | +500 ml for each °C above normal |
| Dry air | +300-500 ml |
Dark color of urine (normal is light yellow)
Dry mouth and thirst
Headache and fatigue
Decreased concentration
Dry skin
Drink clean drinking water. Tea, coffee and juices also count, but water remains the mainstay. Caffeine in moderate amounts (up to 400 mg/day) does not cause dehydration.
See also: Calorie calculator, BMI calculator, Sleep calculator