Daily Water Calculator

A general guideline is 35 ml per kg of body weight. For a 70 kg person, that is 2,450 ml (about 2.45 liters) under normal conditions. Activity level and climate can increase this by up to 40%.

The formula is: weight (kg) × 35 ml × activity multiplier × climate multiplier. Activity multipliers range from 1.0 (sedentary) to 1.4 (very active), and climate multipliers from 1.0 (temperate) to 1.2 (hot). The calculator applies these automatically based on your selections.

Water regulates body temperature through sweat, transports nutrients and oxygen to cells, flushes waste through kidneys, lubricates joints, and supports digestion. Just 1–2% dehydration impairs cognitive performance, endurance, and causes headaches and fatigue.

It depends on intensity. Light activity (30 min walk): multiply your baseline by 1.1. Moderate exercise (gym, running): by 1.2. Intense activity (high-intensity sports): by 1.3–1.4. During intense exercise in heat, you can lose over 1 liter of sweat per hour.

Yes. In temperate climates (15–25 °C) no adjustment is needed. In warm climates (25–35 °C) you need about 10% more. In hot climates (>35 °C) you need about 20% more.

In extreme cases, yes. Hyponatremia occurs when excessive water intake in a short time dilutes blood sodium. Under normal conditions, drinking throughout the day following thirst and calculator recommendations is safe. Avoid large amounts at once.

This is a general estimate. It does not account for kidney disease, heart failure, or medications affecting fluid retention. People with these conditions should follow their doctor's guidance. Persistent thirst and dark urine are signs of dehydration that need attention.