How much water should you drink?

Water is a major component of the human body. On average, about 60% of the adult body is made up of water.

A 70-kg man is made up of around 42 litres of total water, and it will be ~distributed as follows:

1. Intracellular water (within cells) -28 litres

2. Extracellular fluid - 14 litres, comprising of:
Interstitial fluid (lymph included), which is an aqueous medium surrounding cells - 10 litres
Blood plasma- 3 litres
Transcellular fluid (cerebrospinal fluid, ocular, pleural, peritoneal and synovial fluids) - 1 litre

How much water must you drink each day?

Everyday body functions are associated with water loss and this need to be replaced.

The Institute of Medicine (IOM) recommends a daily intake of approximately 13 cups (3 litres) a day for men and 9 cups (2.2 litres) for women.

An easy to remember guide is to drink eight 8-ounce glasses of water daily is drinking 8 by 8, which works out to around 1.9 litres of water, which is close to IOM's recommendation for women.

Calculation based on body weight

Many fitness experts recommended 1/2 ounce of water for each pound of body weight.

So divide your body weight by 2 to get the total quantity of water you have to drink in ounces.

For ex., if you are 180 pounds, you need to take 180/2 = 90 ounces of water

A glass of water is ~ 8 ounces (it can vary depending on the size of the glass).

Therefore divide the total water quantity to drink by 8 to get the number of glasses.

So 90 ounces of water amounts to 90/8 = 11.25 glasses of water.

Adjust for Activity Level

You will need to adjust that amount of water intake based on your activity level and weather as you will lose more water when you sweat, based on how often you workout.

For every 30 min of exercise, you should add additional 12 ounces of water. So if you workout for 1 hour, add 24 ounces of water to your daily intake.

Other factors that can influence water consumption include:
Environmental factors: The indoor or outdoor temperature.
Pregnant and breastfeeding women require additional water to remain well hydrated.
Health conditions like diarrhoea, fever or vomiting may require the intake of oral rehydration solution.

Drink adequate water that you don't feel thirsty often and pass around 1.5 litres of colourless to light yellow urine a day; then you are plausibly well-hydrated. If you are not sure of your water intake needs, reach out to your doctor/dietician.