Climate and Weight Hydration Calculator
Scientific algorithm: 35ml/kg base corrected for temperature, humidity and activity.
Real-time weather: fetches temperature and humidity from your current location.
Mix indicator: tells you whether you need pure water, salted water or electrolytes.
Urine scale: visual monitoring of hydration status.
# Scientific Hydration Guide: How to Calculate Water Intake by Weight and Climate
Hydration is not a one-size-fits-all science. The commonly recommended "two litres of water a day" is a myth that ignores the critical variables that define our fluid homeostasis. For an athlete in the middle of a heat wave, those two litres could be insufficient in just one hour.# The Base Formula: 35 ml per Kilogram
The starting point accepted by sports physiologists and nutritionists is an intake of 35 ml of water per kilogram of body weight for healthy adults under normal conditions. This base ensures that plasma volume remains stable for basic vital functions. However, this is only the hydration "floor"; any external factor will increase this demand.# The Impact of Climate: Temperature and Humidity
When ambient temperature exceeds 30°C, the body must activate its main cooling mechanism: evaporation. For each degree the thermometer rises above this threshold, fluid demand increases by approximately 10%.The Risk of High Humidity
If humidity exceeds 60%, sweat cannot evaporate efficiently. Body temperature rises faster and the body tries to compensate by sweating more. In humid climates, electrolyte loss tends to be greater even if the air does not feel hot.| Climate Variable | Physiological Effect | Recommended Action |
|---|---|---|
| Dry Heat (above 35°C) | Fast evaporation, immediate thirst. | Drink small amounts frequently. |
| Humid Heat (above 30°C) | Inefficient sweat, hyperthermia risk. | Add salts and seek shade/ventilation. |
| Intense Cold (below 5°C) | Loss through breathing and cold diuresis. | Do not wait for thirst (thirst is suppressed). |
# Hydration During Sport and Physical Exertion
During exercise, fluid loss can range from 500 ml to 2 litres per hour. It is not just water; sweat carries sodium, potassium and magnesium. If we only replace water during massive sweat loss, we risk hyponatraemia (excessive dilution of sodium in the blood).# Reading the Urine Colour Scale
- Levels 1-2 (Pale/Light Yellow): optimal hydration. Continue at your current pace.
- Levels 3-4 (Bright Yellow): slightly deficient hydration. Drink a glass of water now.
- Levels 5-7 (Amber/Brown): severe dehydration. Urgent fluid replacement needed.