Water Intake Calculator
Calculate how many liters and glasses of water you should drink daily based on your weight and activity level.
Our free Water Intake Calculator tells you exactly how many liters (and glasses) of water you should drink each day based on your body weight and physical activity level. Proper hydration supports energy levels, brain… Fill in the fields and see your result. Everything is computed on your device—we don't collect or store your inputs.
About This Calculator
Our free Water Intake Calculator tells you exactly how many liters (and glasses) of water you should drink each day based on your body weight and physical activity level. Proper hydration supports energy levels, brain function, digestion, skin health, kidney function, and exercise performance. Dehydration — even as little as 2% of body weight — can cause fatigue, headaches, and reduced concentration. Enter your weight and select your activity level to get a personalized daily water target you can follow easily.
How It Works
The calculator uses a base requirement of 35 ml per kilogram of body weight, which aligns with general medical guidelines. It then adjusts for activity level: Sedentary (x1.0) for desk work with minimal exercise, Lightly Active (x1.2) for light exercise a few days a week, Moderately Active (x1.5) for regular workouts, and Very Active (x2.0) for intense daily training or physical labor. The result is displayed in liters and converted to approximate glasses (assuming 250 ml per glass) for easy daily tracking.
How to Use
- Enter your values in the calculator fields above
- Click the calculate button or let the calculator auto-update
- Review your results instantly
- Adjust values as needed to see different scenarios
Frequently Asked Questions
How much water should I drink every day?
A widely used guideline is 35 ml per kg of body weight. For a 70 kg person that is about 2.45 liters (roughly 10 glasses) at a sedentary level. Active individuals, people in hot climates, and pregnant or breastfeeding women generally need more. This calculator adjusts for your activity level automatically.
Does coffee, tea, or juice count toward my water intake?
All fluids contribute to hydration, including coffee, tea, milk, and juice. However, caffeinated drinks have a mild diuretic effect, and sugary beverages add empty calories. Plain water remains the best choice for meeting your daily target.
Does the water in food count?
Yes. Many foods — especially fruits (watermelon, oranges), vegetables (cucumber, lettuce), and soups — contain significant water. On average, food provides about 20% of daily water intake. This calculator focuses on fluid intake (drinking water), so food water is a bonus on top of your target.
What are the signs of dehydration?
Early signs include thirst, dark yellow urine, dry mouth, fatigue, and headache. More severe dehydration can cause dizziness, rapid heartbeat, confusion, and reduced urination. A simple check: if your urine is pale yellow, you are likely well-hydrated.
Should I drink more water during exercise?
Yes. Drink about 500 ml (2 glasses) two hours before exercise, sip 150-250 ml every 15-20 minutes during exercise, and drink 500 ml or more after exercise to replace sweat losses. For intense sessions longer than an hour, consider an electrolyte drink to replace sodium and potassium lost through sweat.
Why Use Our Free Water Intake Calculator Online?
Our Water Intake Calculator gives you a quick, private check without an account. Enter your details and get an instant result. All processing happens locally, so we don't see or store your health-related inputs. For medical decisions, always consult a healthcare provider; this tool is for general guidance only.