Water Intake Calculator
Find how much water to drink each day.
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Enter your details and press calculate to see your result.
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Your daily water intake is the total amount of fluid your body needs each day to replace what it loses through urine, sweat, breathing and digestion. Staying hydrated keeps your blood volume, body temperature and joint lubrication where they should be, and even mild dehydration can leave you tired, headachy and weaker in the gym. This calculator estimates how much water to drink per day from your bodyweight and your exercise, and shows the result in both litres and 250 ml glasses so the target is easy to hit.
How your water target is calculated
We use a simple, widely cited rule: about 35 ml of water per kilogram of bodyweight per day. That base figure covers a normal day with no heavy sweating. On top of it we add roughly 350 ml for every 30 minutes of exercise, because training raises your sweat losses and those need to be replaced. If you enter your weight in pounds, it is converted to kilograms first.
For example, an 80 kg person who does not train needs about 80 multiplied by 35, or 2,800 ml a day, which is 2.8 litres. Add one hour of exercise and you add two 350 ml portions, bringing the total to 3,500 ml, or 3.5 litres. At 250 ml per glass that is about 14 glasses spread across the day.
Use it as a guide, not a hard rule
No formula can capture everything that changes your needs. Hot or humid weather, high altitude, a fever, pregnancy, a high-salt or high-protein diet and a heavy sweat rate all push the number up, so treat the result as a sensible starting point and drink more when conditions demand it. The most reliable feedback comes from your body: pale-yellow urine usually means you are well hydrated, while dark urine and persistent thirst mean you are behind.
Other drinks and food count toward the total too. Tea, coffee, milk and water-rich foods like fruit and soup all contribute fluid, so you do not need to reach the whole target from plain water alone, though water remains the easiest and cheapest way to top up. Spreading intake evenly through the day absorbs better than drinking large amounts at once, and overshooting by a glass or two is harmless for healthy people.
How to use
- 01
Enter your weight
Type your bodyweight in kilograms or pounds.
- 02
Add exercise time
Include your daily exercise minutes to account for sweat losses.
- 03
See your target
Get your daily water goal in litres and 250 ml glasses.
Frequently Asked Questions
A common guide is about 35 ml per kilogram of bodyweight, plus extra for exercise, heat and altitude.
Yes. Tea, coffee and food all contribute to hydration, though plain water is the easiest way to hit your target.
Rarely, but drinking extreme amounts quickly can dilute blood sodium. Spread intake across the day.
Pale-yellow urine is a good sign. Dark urine and thirst suggest you need more fluids.
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Last reviewed June 2026 · Methodology & sources