I bet you have read drink 8 glasses of water in your science books when in school. The information is so vague. There is no mention of the volume of the glass, kind of water, the temperature of water, ph value of water and so many other things that will confuse you.

Ideally, an average person should drink 2 liters of water. So that would 250 ml per glass. In India glasses are 300ml and above. I have a steel glass that is 550 ml. So one should always talk in liters and not the number of glasses when trying to calculate how much water to drink. 250ml * 8 glasses = 2 liters. But, an average person does not consider age, height, weight, gender, and health conditions. So this rule is little faulty.

I know that when one is healthy and fit, which means when one is not fat, obese, disease free then one should drink water based on the body weight.

A 100kg man will have to drink more than a 50 kg man. Right.

An obese person trying to lose fat will have to drink more than a healthy person. Right.

An adult will have to drink more than a toddler or a baby. Right.

A person with diseases where water is not flushed out easily will have to drink less. Right.

A person with heart or kidney diseases will have to check very precisely how much water has to be taken else, either of the two organs or both will start to go off track. Right

If you have other food that is watery then that water is also added to the volume you drank. Right.

Drinking plain water is retained less than that mixed with a pinch of salt or lemon juice. Right.

Why? Why then the books never mentioned these! Why has such a blind following of water intake been prevailing since ages? Ram Jaane.

These are a few ways to calculate how much water you must consume.

1. Base level water. Weight in Kg *2.2 * 2/3 * 33/1000 = Amount of water in Litres you have to drink per day. Or just multiply your body weight in kg by 0.05. So if your weight is 60Kg, you must drink 60*0.05 = 3 Litres per day.
2. Other liquid intake. Now let us say you drink tea/ coffee/ milk /juice/ chaas/ lassi/ lime water/ dal/ curd etc which has water in it, you must consider them too in the total water. So if your base level for water is 3 liters, minus the tea, chaas, curd, lime water from 3 liters which could be 500ml or 750ml lesser. Hence your actual water intake will reduce to 2.5 Lt or 2.25 Lt.
3. If you have to lose fat or exercise more or you go to the gym or you run every day, then you should increase the water level by 2 to 3 liters on top of the base level. So you will drink Base level plus 2 liters. Hence Base level – other liquid intakes + 2 liter is your actual water intake.

So a simple calculator for water intake:

((Body wt in Kg * 0.05) +1.5) = (60*0.05 + 1.5) Liters = Weight * 6.75% or 7%

Remember:  If you workout, gym, run or want to lose fat = 7% of your body weight in Kg, is the water intake.

Else for a normal healthy person, it’s 5% of your body weight that must be water intake minimum per day. Incidentally, your blood volume is 5% of your body weight. 🙂