Daily Water Intake Calculator

Estimate how much water to drink per day from your weight, daily exercise and the weather, in litres and in glasses. Enter your values; the result updates as you type, with the method shown below.

About this calculator

Daily water needs depend on body weight, activity and climate. This calculator gives a practical estimate of how much to drink, based on about 33 ml per kilogram, plus extra for exercise and hot weather.

Enter your weight, your exercise time and whether it is hot. The calculator shows the water to drink per day and the equivalent in glasses.

When to use it

  • Setting a daily drinking goal.
  • Adjusting intake on training days.
  • Preparing for hot weather or travel.
  • Helping someone who forgets to drink.

How to read the result

Food provides about 20% of daily water, which is why the estimate covers drinks only. Thirst and pale urine are good everyday guides.

People with heart or kidney conditions may have limits set by their doctor.

Mistakes to avoid

  • Drinking large amounts very quickly.
  • Ignoring extra needs during exercise or heat.
  • Following the estimate when a doctor has set a limit.

Formula

Water = 33 ml × weight + 350 ml per 30 min of exercise + 0.5 L if hot

Worked example

70 kg with 30 minutes of exercise: about 2.7 litres a day, or 11 glasses.

Frequently asked questions

Do other drinks count?

Yes, and food provides about 20% of daily water.

Is more always better?

No; very large amounts can be harmful.

Who should ask a doctor?

People with kidney or heart disease.

Do tea and coffee count?

Yes, they contribute to hydration.

Can I drink too much?

Yes, very large amounts in a short time can be dangerous.

How do I know I drink enough?

You rarely feel thirsty and your urine is pale yellow.

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Results are estimates for information only. Check important figures with a professional.