Daily Water Intake Calculator
Calculate your daily water needs by weight and activity level.
How Much Water Should You Drink Per Day? Calculate by Weight
You have probably heard the "everyone should drink 8 glasses of water" rule. The problem is that this rule ignores the difference between 60 kg and 100 kg, activity level, or hot weather. The daily water intake calculator lets you set a personal target based on your weight and lifestyle.
What Is a Water Intake Calculator and Why Do You Need One?
Roughly 60% of the body is made up of water. Water is critical for nutrient transport, temperature regulation, and waste elimination. Insufficient water intake can manifest as difficulty concentrating, headaches, and fatigue.
The standard "2 litre" recommendation is based on an average adult. For an active person it may be insufficient, while for a small-framed sedentary person it may be too much. The calculator corrects for this difference using a formula of 35 ml per kilogram of body weight.
How to Use It. Step by Step
Required Inputs
- Your weight (kg)
- Activity level (sedentary → very active)
- Hot / humid weather (yes / no)
Formula and Calculation Logic
Base need: Weight (kg) × 35 ml. An addition is made based on activity level: lightly active +350 ml, moderately active +700 ml, very active +1,050 ml. In hot or humid weather an extra +500 ml is added due to additional sweating.
Example Scenarios
| Scenario | Total (ml) | Glasses (200 ml) | Bottles (500 ml) |
|---|---|---|---|
| 60 kg, sedentary, normal weather | 2,100 ml | 11 | 4.2 |
| 75 kg, moderately active, normal weather | 3,325 ml | 17 | 6.7 |
| 90 kg, active, hot weather | 4,700 ml | 24 | 9.4 |
| 55 kg, lightly active, hot weather | 2,775 ml | 14 | 5.6 |
This tool is for informational purposes only. If you have kidney disease or other medical conditions, consult a doctor regarding your daily fluid needs.
How to Interpret Your Results
The calculator gives you a total daily target. You can meet this amount not only through water you drink, but also through the water contained in tea, juice, and foods such as vegetables and fruit. Solid foods cover approximately 20% of daily water needs.
Urine colour is a good indicator: light yellow is ideal, while dark yellow or orange signals that you need to drink more. Treat the calculator result as a minimum target, not an upper limit.
Tips for Accurate Results
- Enter your morning weight; fluctuations throughout the day can affect the calculation.
- Be realistic about your activity level: if you exercise 3 days a week, choose the 'lightly active' option.
- On days with intense exercise, you can increase the result by 15–20%.
- Caffeinated beverages (coffee, tea) are mildly diuretic; be cautious when counting them toward your daily water goal.
Frequently Asked Questions
Enter your weight, select your activity level and find out your daily water target in seconds. Note the result to track your intake, or use your phone's alarm to remind yourself to drink every 2 hours.