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Calculation Machine

Daily Water Intake Calculator

How much to drink for your weight, climate and training.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Daily water target
106 oz
In litres
3.13 L
Standard 16 oz bottles
6.6
8 oz glasses
13.3

Quick answer

A common baseline is half your body weight in ounces of water per day, plus 12–16 oz for every 30 minutes of exercise.

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Body weight170 lb
  • Exercise45 minutes/day
  • ClimateTemperate

Result

  • Daily water target106 oz
  • In litres3.13 L
  • Standard 16 oz bottles6.6
  • 8 oz glasses13.3

How to use the Daily Water Intake Calculator

  1. 1Enter your body weight.
  2. 2Add daily exercise minutes.
  3. 3Pick your climate to adjust the target.

Frequently asked questions

Do coffee and tea count?

Yes. Caffeinated drinks are mildly diuretic but still contribute net fluid to your daily total.

How do I know I'm hydrated?

Pale straw-coloured urine and infrequent thirst are the simplest day-to-day indicators.

About this calculator

How much water you actually need

There is no single number for everyone. Needs rise with body size, heat, altitude and exercise, and a good share — around 20% — comes from food. The calculator gives a starting estimate based on body weight and activity.

For most healthy people, thirst and pale-yellow urine are reliable guides. The estimate is most useful on hot days, during long training sessions, or if you tend to forget to drink.

Practical hydration

  • Add roughly 400–800 mL per hour of moderate exercise, more in heat.
  • Tea, coffee, milk and water-rich food all count toward intake.
  • Drinking very large amounts quickly can be dangerous; spread intake through the day.
  • People with heart, kidney or liver conditions should follow their clinician's fluid advice instead.

Sources

More questions

Is 8 glasses a day a real rule?

It is a rough rule of thumb, not a scientific requirement. Many people need more or less.

Does coffee dehydrate you?

Not in normal amounts. The fluid in coffee more than offsets its mild diuretic effect.