I am planing to develop a mobile application to monitor the water intake level of a person. I found the following calculator, but I have no idea what is the formula that they have used in the calculator.


I want to create a formula to determine how much water to drink per day using following inputs.

  • Age
  • Weight
  • Height
  • Gender
  • Activity(No of hours)

Can any one suggests me a formula for this

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    – Carey Gregory
    Apr 6, 2020 at 18:24
  • 1
    The formula is: "When you are thirsty, drink some water.". That's far more reliable than any calculations you can make. A slight improvement would be to add: "If you've been sweating, add a pinch of salt to it." Apr 7, 2020 at 0:44
  • 1
    It's like you asked Newton why you didn't eat the apple instead of finding a formula. You live in 21st century Apr 7, 2020 at 5:52
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    Whatever formula that website uses, it's wrong. The site asks about exercise on a per-week basis, while hydration level fluctuates on a timescale of less than a day. (It also asks how often you exercise, when it should be asking how hard you exercise.)
    – Mark
    Apr 8, 2020 at 0:27

1 Answer 1


No, because activity as a feature is too highly variant and there are probably a lot of other factors that would go into a formula like this.

If you do a bit of research you will find that there are guidelines of fluid intake per day for certain groups of patients, e. g. in intensive care, dialysis patients,...: https://www.ncbi.nlm.nih.gov/pubmed/?term=fluid+intake+per+day

The first hit on "formula fluid intake per day" produces a hit from the Daily Mail (https://www.dailymail.co.uk/femail/food/article-4617270/How-water-REALLY-drink-day-revealed.html), which does not have too high of an impact factor.

The "8 glasses of water per day" rule is a one-size-fits-all rule that should not be used on people with e. g. organ damage such as heart failure, renal failure etc.

  • I want to develop a similar calculator like this. gigacalculator.com/calculators/water-intake-calculator.php . Apr 6, 2020 at 18:41
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    @AmilaDulanjana Ambient temperature and humidity are potentially huge factors and you're ignoring them. The amount of water you need on a winter day in Norway wouldn't keep you alive in the Sahara desert on a summer day. As I said in my comment on your question, you need to do a little research on your own and add what you find to your question.
    – Carey Gregory
    Apr 6, 2020 at 19:33
  • I don't understand why do you want to make this solution more complicated. This is a MVP solution and we can include these features later. Moreover any one knows how to calculate the BMI index of a person, but it's not accurate. But everyone is using it to get an idea. So if you dont know the real answer it's better not to give opinion like this. Apr 7, 2020 at 5:56
  • @AmilaDulanjana, if you don't include those complexities, your minimum product won't be viable.
    – Mark
    Apr 8, 2020 at 0:19

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