How much water should you drink per day?

What the Daily Water Intake Calculator Does

This calculator estimates how much water you should aim to drink each day based on your body weight. Enter your weight, and it returns a daily target in liters (and the equivalent in cups or milliliters).

It's useful for anyone who wants a simple, personalized starting point for hydration: office workers, students, casual exercisers, and people who simply forget to drink enough. It is a general guideline, not medical advice. If you have a kidney condition, heart failure, or are pregnant, follow the fluid targets your doctor gives you instead.

How It Works: The Hydration Formula

The calculator uses a common weight-based rule of thumb. For each kilogram of body weight, it allocates about 33 milliliters of water:

liters per day = body weight (kg) x 0.033

If you enter your weight in pounds, the tool first converts it to kilograms (1 lb = 0.4536 kg) before applying the formula. The 0.033 factor is an average; the result describes total daily target, which includes water from food and other drinks, not just plain water from a glass.

Worked Example

Suppose you weigh 70 kg. The calculation is:

70 x 0.033 = 2.31 liters per day.

That's roughly 2,310 mL, or about 9 to 10 standard 240 mL cups. For someone weighing 154 lb (the same 70 kg), the tool converts first: 154 x 0.4536 = 69.85 kg, then 69.85 x 0.033 = 2.30 liters. A lighter 55 kg person would aim for 55 x 0.033 = 1.82 liters, while a 90 kg person would target 90 x 0.033 = 2.97 liters.

Factors That Change Your Real Need

The formula gives a baseline. Your actual requirement rises or falls depending on circumstances:

• Exercise: Add roughly 350 to 700 mL for each hour of moderate activity to replace sweat losses.
• Climate: Hot or humid weather and high altitude increase fluid loss, so you need more.
• Diet: High-salt, high-protein, or high-fiber meals raise water needs; fruits and vegetables supply extra water.
• Health status: Fever, vomiting, or diarrhea increase losses, while some medical conditions require restricting fluids.
• Caffeine and alcohol: These have a mild diuretic effect, especially in large amounts.

Practical Tips and Common Mistakes

A reliable everyday signal is urine color: pale straw means you're well hydrated, while dark yellow suggests you need more. Don't rely on thirst alone, since it tends to lag behind actual need.

A frequent mistake is treating the target as plain water only. Food typically provides about 20 percent of daily fluid intake, and tea, milk, and juice all count. Another error is drinking a large amount all at once; spreading intake across the day is gentler and more effective. Finally, more is not always better. Drinking far beyond your needs can dilute blood sodium (hyponatremia), so use the result as a guide rather than a rigid quota.