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Water Intake Calculator

Estimate how much water to drink each day.

Units
kg
minutes

Aim to drink about

This is drinking water and other drinks. Food provides roughly another 20% of the water you need. Thirst and pale yellow urine are good everyday guides.

Results are estimates for general information only and are not medical advice. Talk to a doctor or other qualified health professional about your health. Read our disclaimer.

When to use it

Use this calculator to get a personal daily water target instead of a one-size-fits-all rule. It is helpful when you start a new exercise routine, travel somewhere hot, are pregnant or breastfeeding, or simply want a number to aim for with a water bottle.

How to use it

  1. Choose your Units: kg and liters or lb and ounces.
  2. Enter your Body weight.
  3. Enter your Exercise per day in minutes.
  4. Choose your Climate: Mild or cool or Hot or humid.
  5. Tick Pregnant or breastfeeding if it applies.
  6. Read the amount under Aim to drink about, shown in liters or ounces and as a number of glasses.

How it works

The tool starts with about 33 ml of water for every kilogram of body weight. It adds about 350 ml for every 30 minutes of exercise, 500 ml for a hot or humid climate, and 700 ml if you are pregnant or breastfeeding. Food provides roughly another 20% of the water you need, so this target covers drinks only.

Worked example

You weigh 70 kg and walk for 30 minutes a day in a mild climate. The tool suggests about 2.7 liters a day, roughly 11 glasses of 250 ml, or 90 fl oz.

On a hot summer day, choose Hot or humid and the target goes up by about half a liter. If you add a one-hour run, enter 90 minutes of exercise in total and the target rises by another 700 ml. Using US units instead, a 154 lb person gets the same advice in fluid ounces.

Tips

  • Spread it out. Drink a glass with each meal and one between meals rather than a lot at once.
  • Use a marked bottle. Knowing your bottle holds 750 ml makes it easy to count: about four refills for 2.7 liters.
  • Drink before you exercise. Have a glass 30 minutes before a workout and sip during long sessions.
  • Eat water-rich foods. Fruit, vegetables and soups help you reach your total.

Common mistakes

  • Waiting until you are very thirsty. By then you may already be a little dehydrated, especially in the heat.
  • Forgetting to adjust for exercise. Heavy sweating can lose a liter or more an hour.
  • Treating the target as a strict rule. It is a guide. Listen to your body and drink more when you are hot, ill or active.

This is a general guide, not medical advice.

Frequently asked questions

Do tea, coffee and other drinks count?

Yes. All drinks count towards the total, including tea, coffee and milk. Caffeine has a mild effect, but regular coffee drinkers still gain most of the water. Sugary drinks and alcohol are best kept to a minimum.

Why is the 8 glasses a day rule not used?

It is easy to remember but does not fit everyone. A larger or more active person needs more, and a smaller person in a cool climate may need less. This tool adjusts for weight, exercise, climate and pregnancy.

Can I drink too much water?

Yes, though it is rare. Drinking very large amounts quickly, especially during long endurance events, can lower the salt level in your blood. Spread your drinks through the day and drink to thirst.

How do I know if I am drinking enough?

Pale yellow urine and not feeling thirsty are good everyday signs. Dark urine, headaches and tiredness can be signs you need more.

Should people with health conditions follow this?

Not without advice. Some heart and kidney conditions need limits on fluid. Follow your doctor's guidance if you have been told to limit or increase how much you drink.

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