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SnapCalculations

Water Intake Calculator

Enter your weight and daily exercise to get a daily water estimate, with the U.S. National Academies guideline shown for comparison.

Sex
Weight in
kg
min

Water per day

2.8 L

About 11 glasses of 250 ml

US cups (8 fl oz)
11.8
US fluid ounces
95
Millilitres
2,800 ml
U.S. guideline for men (all drinks)
3 L

A rule-of-thumb estimate. Hot weather, illness, pregnancy and breastfeeding raise your needs; some heart and kidney conditions lower them.

Step-by-step solution

Worked out with your numbers. Change any value above and the steps update.

  1. 1

    Base need: 35 ml per kg of body weight

    70 × 35 = 2,450 ml

  2. 2

    Exercise: 350 ml for every 30 minutes

    30 ÷ 30 × 350 = 350 ml

  3. 3

    Total per day

    2,450 + 350 = 2.8 L

How it works

  • A common rule of thumb is 35 ml of water per kg of body weight per day.
  • Add about 350 ml for every 30 minutes of exercise to replace sweat losses.
  • For comparison, the U.S. National Academies suggest about 3.0 L of drinks a day for men and 2.2 L for women; food supplies roughly a further 20% of water.

Worked examples

70 kg with 30 minutes of exercise

How much water should a 70 kg person who exercises 30 minutes a day drink?

  1. Base: 70 × 35 ml = 2,450 ml.
  2. Exercise: 350 ml per 30 minutes = 350 ml.
  3. Total = 2,800 ml.

Answer: About 2.8 litres (11 glasses)

Try this example

11 stone with an hour of exercise

How much water does someone weighing 11 stone need on a day with 60 minutes of exercise?

  1. 11 st = 154 lb = 69.85 kg.
  2. Base: 69.85 × 35 = 2,445 ml; exercise: 2 × 350 = 700 ml.
  3. Total = 3,145 ml.

Answer: About 3.1 litres (13 glasses)

Try this example

Frequently asked questions

Do tea, coffee and other drinks count?

Yes. All drinks count toward your fluid intake, and so does water in food such as fruit and soup.

Can you drink too much water?

Yes. Drinking very large amounts in a short time can dangerously lower sodium levels. Spread drinks through the day and let thirst guide you.

Results are estimates for general information and are not financial, medical or professional advice.