Daily Water Intake for a 40 kg Person
A 40 kg person needs approximately 1.4–1.8 litres of water per day at baseline activity.
How to use this tool
- Enter body weight and activity level in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your water per day and the full breakdown beneath it.
Calculate the daily water intake for a lighter individual or teenager weighing 40 kg.
Frequently asked questions
- How much water should I drink per day?
- The NHS recommends 6–8 cups (1.5–2 L) daily. The 35 ml/kg rule adjusts this for body size and is widely used by dietitians.
- Does coffee or tea count towards water intake?
- Yes — caffeinated drinks count towards hydration despite mild diuretic effects. Fruit and vegetables also contribute significant water.