Stax

Water Intake Calculator

Calculate daily water intake based on body weight and activity level.

Why does daily water intake matter?

Water makes up about 60% of the human body and is involved in every physiological process — temperature regulation, nutrient transport, joint lubrication, digestion, and toxin removal. Even mild dehydration (1–2% of body weight) can impair concentration, increase fatigue, and reduce physical performance.

How the calculation works

This calculator uses the widely accepted base rate of 35 ml per kg of body weight, then applies two multipliers: one for activity level and one for climate. The resulting number represents total daily fluid intake from all sources — water, beverages, and food.

Tips for staying hydrated

  • Start the day with a large glass of water before coffee or tea.
  • Keep a 1-litre bottle visible on your desk as a visual reminder.
  • Drink a glass before each meal — it also helps with portion control.
  • Set a phone reminder for the afternoon slot (2–5 PM), the most common time for dehydration and energy dips.
  • Avoid large amounts right before bed to prevent sleep disruption.

Frequently asked questions

How much water should I drink per day?
General guidelines suggest about 35 ml per kg of body weight as a baseline, adjusted for activity and climate. For a 70 kg moderately active person in a temperate climate, that is approximately 3.0–3.1 litres per day. The popular '8 glasses a day' rule is a rough approximation.
Does the total include water from food?
Yes. The recommendation accounts for all fluid sources, including approximately 20% that typically comes from food (fruits, vegetables, soups). You do not need to drink the full calculated amount as plain water — other beverages count too.
How does activity level affect water needs?
Exercise and physical labour cause sweating, which increases water loss. A sedentary person needs the baseline amount, while someone doing intense daily exercise (athletes, labourers) can need 60–65% more fluid to stay adequately hydrated.
Why does climate matter for hydration?
Hot and humid climates increase sweat rate significantly. In a hot dry climate, you lose more water through sweat and respiration. In humid heat, sweat evaporates more slowly and you may feel thirsty less but still need more water.
How do I know if I am dehydrated?
The simplest indicator is urine colour. Pale yellow (like lemonade) means well-hydrated. Dark yellow or amber means dehydration. Other signs include dry mouth, fatigue, dizziness, and headache. Drink more water if urine is dark.

Related tools