Thirst is a poor indicator of hydration needs, specially while exercising. Simple way to calculate your hydration needs. Start by multiplying your weight in kg with .033. So for me at 67 kgs daily need is 2.2 ltrs in a day. This may vary substantially depending on temperature, humidity and how heavy your day is like resting to heavy work. And can go upto 10 ltrs also. But basic starting point is what’s mentioned above.

30% of your water needs usually come from your drinks like tea, juice etc. 20% from food. This also can be a variable depending on how much whole or processed food you eat. Vegetables have 90% water & fries have 3%. So adjust according to your diet, lifestyle and environment.

Hydration during exercise- We can sweat 1-5 pounds during exercise depending upon intensity. And this needs to be compensated with drinking water regularly during your workout. If you lose water of 2-3% body weight, your performance can go down drastically, as much as even 20-30%.

Most of us under-drink during exercise. Also understand we aren’t losing water but sweat. So we need to replenish with sweat. Sweat is Na, Cl, K, Mg. And we need some glucose too. So we need to drink some sort of electrolytes rich water. I add 100 gms to 1 ltr water and drink during my workout. Here is a very practical tool kit to find out your hydration needs from my Guru Andy Galpin.