Calculate Your Optimal Daily Hydration Needs Based on Weight & Activity
Our water intake calculator uses a common rule of thumb based on your body weight and physical activity level. The base recommendation is 30ml per kg of body weight, adjusted upward for higher activity levels.
A water intake calculator (also called a hydration calculator or daily water calculator) is a free online tool that determines your optimal daily fluid consumption based on your body weight and physical activity level. Proper hydration is crucial for maintaining energy levels, supporting digestion, regulating body temperature, and promoting overall health.
Water makes up approximately 60% of your body weight and is essential for virtually every bodily function. The general recommendation of drinking 8 glasses (2 liters) per day is a rough estimate. Our calculator adjusts a simple rule of thumb for your body weight and your activity level; it cannot measure how much you actually sweat.
Staying adequately hydrated offers numerous health benefits. Use our water consumption calculator to ensure you're drinking enough water every day.
Meeting your daily water goal doesn't have to be difficult. Here are practical tips to stay hydrated throughout the day:
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Try It →Calculate your optimal daily hydration needs based on weight and activity level. You're here now!
Current ToolQuick answer: enter your weight in kilograms and pick your activity level. The calculator multiplies your weight by 30 to 40 ml, depending on activity, and shows your daily water target in liters, cups and glasses. For a 70 kg person who is lightly active, that is about 2.3 liters.
Daily water (ml) = weight in kg × a factor that rises with activity: 30 ml for sedentary, 33 ml for lightly active, 35 ml for moderately active and 40 ml for very active.
| Weight (kg) | Sedentary (30 ml/kg) | Light (33) | Moderate (35) | Very active (40) |
|---|---|---|---|---|
| 50 | 1.5 L | 1.6 L | 1.8 L | 2.0 L |
| 60 | 1.8 L | 2.0 L | 2.1 L | 2.4 L |
| 70 | 2.1 L | 2.3 L | 2.5 L | 2.8 L |
| 80 | 2.4 L | 2.6 L | 2.8 L | 3.2 L |
| 90 | 2.7 L | 3.0 L | 3.1 L | 3.6 L |
| 100 | 3.0 L | 3.3 L | 3.5 L | 4.0 L |
This is a common rule of thumb, not a medical prescription. Health authorities give general daily fluid guidelines for adults that include water from food and all drinks.
Heat, humidity, high altitude, long exercise sessions, fever, vomiting or diarrhea, pregnancy and breastfeeding can all raise fluid needs. If you have a medical condition, ask your doctor how much you should drink.
It gives an estimate from weight and activity only. It does not know your health, diet, climate or medicines. It is for general information, not medical advice. See our disclaimer.
How much water should I drink a day?
There is no single right amount. A common rule of thumb is about 30 ml per kilogram of body weight for someone who is not very active, more if you are active. For a 70 kg person that is about 2.1 liters. Needs also depend on weather, diet, health and medicines.
How does this calculator work out my water target?
It multiplies your weight in kilograms by 30 ml (sedentary), 33 ml (lightly active), 35 ml (moderately active) or 40 ml (very active), then shows the result in liters, cups and glasses.
Does food and other drinks count?
Yes. Water in food, tea, coffee, milk and other drinks all contribute to your fluid intake. Many people get a fair share of their fluid from food.
How many glasses is 2 liters?
About 8 glasses of 250 ml, or about 8 to 9 cups of 240 ml (8 oz).
Do I need more water in hot weather or when I exercise?
Usually yes. You lose more fluid through sweat. Drink steadily through the day and drink more around exercise, heat and high altitude.
What are signs I am not drinking enough?
Thirst, dark yellow urine, headache, dry mouth and tiredness are common signs. Pale yellow urine usually means you are drinking enough.
Can I drink too much water?
Yes, though it is uncommon. Drinking very large amounts in a short time can dilute the sodium in your blood. Spread your drinks through the day and drink to thirst.
Who should not rely on a calculator?
People who are pregnant or breastfeeding, who have kidney, heart or liver conditions, or who take medicines that affect fluid balance should follow their doctor's advice on fluids.
Why is the weight in kilograms?
The formula uses kilograms. To convert pounds, divide by 2.2. For example, 154 lb is about 70 kg.