Daily Water Intake Calculator
Estimate your recommended daily water intake in litres based on body weight and activity level, using a standard hydration guideline.
Your results
General hydration guideline only; individual needs vary with climate, health and sweat rate.
Calculation breakdown
- Base intake
- Base (mL) = body weight (kg) × 33
- Activity add-on
- Total = base + activity allowance (0–1,000 mL depending on activity level)
Worked example
A 78 kg person with a moderate activity level has an estimated daily water need of about 3.1 litres, combining a base of 2.57 L plus a 500 mL activity allowance.
Assumptions
- Uses a common guideline of 33 mL per kg of body weight per day.
- Does not separately account for climate, illness or breastfeeding, which can increase fluid needs.
How this calculator works
This calculator estimates a general daily water intake target in litres, based on your body weight and how much extra fluid you may need for exercise or hot conditions. It applies a common hydration guideline of around 33 millilitres per kilogram of body weight per day, plus an allowance for activity level.
Frequently asked questions
How is the base water target calculated?
It uses a common guideline of roughly 33 millilitres of water per kilogram of body weight per day as a starting point.
Does exercise increase how much water I need?
Yes, this calculator adds extra fluid for higher activity levels to account for sweat losses during exercise.
Does this include water from food?
No, this estimates total fluid intake from drinks; roughly 20% of daily water intake typically comes from food.
Results are estimates only and are not financial, tax, legal or credit advice.