Water Intake Calculator
Results are estimates only and may not reflect your individual needs. This tool is for educational purposes only and is not medical advice.
Estimate how much water you should drink daily based on your weight, age, and activity level.
Your result will appear here
Complete the form and press Calculate Water Intake.
Estimated result
Daily hydration needs vary with climate, health, and individual factors.
Why use this calculator
Hydration affects energy, performance, digestion, and appetite regulation. Most people underestimate how much water they need — especially on active days or in warm weather. This calculator personalises your daily target based on your weight, age, and activity level.
How to use this calculator
Enter your weight and age, then choose your typical activity level. Press Calculate to see your estimated daily water intake in litres, millilitres, and glasses.
What the result means
The base estimate uses 35 ml per kg of body weight, a widely cited guideline. This is adjusted slightly downward for age over 55 and upward for higher activity levels. One glass is counted as 250 ml.
Important limitations
Actual hydration needs vary with climate, sweat rate, diet water content, health conditions, and medications. Coffee, tea, and food all contribute to daily fluid intake.
FAQ
Does coffee count toward my water intake?
Yes — despite being mildly diuretic, caffeinated drinks still contribute to daily fluid balance for most people.
Should I drink more when exercising?
Add roughly 500–1000 ml per hour of moderate exercise, more in heat.
Why does age affect my water needs?
Water requirements decrease slightly after age 55 as kidney function and thirst sensation change. The calculator applies a small downward adjustment for older adults to reflect this physiological shift.
These estimates are for educational purposes only and are not medical advice. They are not intended for children, teens, pregnancy, eating disorder recovery, or medical conditions.