You may have heard that it’s important to drink plenty of water every day to stay healthy.
Water is, of course, important. Making up around two-thirds of our body weight, water carries nutrients and waste products around our bodies, regulates our temperature, acts as a lubricant and shock absorber in our joints and plays a role in most chemical reactions happening inside us.
The body constantly loses water throughout the day, mostly through urine and sweat but also from regular body functions like breathing. To prevent dehydration, you need to get plenty of water from drink and food every day.
WHY DO WE NEED TO DRINK WATER?
Water is your body’s principal chemical component and makes up about 50% to 70% of your body weight. It keeps every system in the body functioning properly.
Your body depends on water to survive. Every cell, tissue and organ in your body needs water to work properly. Water has many important jobs, such as:
- carrying nutrients and oxygen to your cells
- flushing bacteria from your bladder
- aiding digestion
- preventing constipation
- normalizing blood pressure
- stabilizing the heartbeat
- cushioning joints
- protecting organs and tissues
- regulating body temperature
- maintaining electrolyte (sodium) balance.
Lack of water can lead to dehydration — a condition that occurs when you don’t have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.
HOW MUCH WATER SHOULD YOU DRINK EVERY DAY
How much water should you drink each day? It’s a simple question with no easy answer.
Your individual water needs depend on many factors, including your health, how active you are and where you live.
No single formula fits everyone. But knowing more about your body’s need for fluids will help you estimate how much water to drink each day.
Average daily intake of fluids
So how much fluid does the average, healthy adult living in a temperate climate need? The U.S. National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:
- About 15.5 cups (3.7 liters) of fluids a day for men
- About 11.5 cups (2.7 liters) of fluids a day for women
These recommendations cover fluids from water, other beverages and food. About 20% of daily fluid intake usually comes from food and the rest from drinks.
“8×8 rule” of drinking water per day
Have you heard of the 8×8 rule? This rule is a relatively simple rule of thumb to follow if you choose to do so. The unofficial advice recommends we drink eight eight-ounce (240 ml) glasses of water every day, totalling just under two liters, on top of any other drinks.
It doesn’t specify whether or not they should be broken up throughout the day, consumed in the morning or night, or how fast they should be consumed. Essentially, as long as you get the specific amount of water in your system throughout the day, nothing else matters according to this rule.
However, his rule doesn’t have much (or any) scientific backing. There has been no research conducted to discover the benefits of consuming eight eight-ounce glasses of water per day. Water consumption varies on the individual and should be customized to specific needs. But still, this rule does come in handy, sometimes.
Amount of water according to your weight
To understand how much water to drink every day, here are the recommended amounts for a range of weights. Remember to mind your activity level too.
pounds / kilogram
ounces / liter
|100 lb / 45,4 kg||50 oz / 1,4 L|
|110 lb / 49,9 kg||55 oz / 1,6 L|
|120 lb / 54,4 kg||60 oz / 1,7 L|
|130 lb / 59,0 kg||65 oz / 1,8 L|
|140 lb / 63,5 kg||70 oz / 2,0 L|
|150 lb / 68,0 kg||75 oz / 2,1 L|
|160 lb / 72,6 kg||80 oz / 2,3 L|
|170 lb / 77,1 kg||85 oz / 2,4 L|
|180 lb / 81,6 kg||90 oz / 2,6 L|
|190 lb / 86,2 kg||95 oz / 2,7 L|
|200 lb / 90,7 kg||100 oz / 2,8 L|
|210 lb / 95,3 kg||105 oz / 3,0 L|
|220 lb / 99,8 kg||110 oz / 3,1 L|
|230 lb / 104,3 kg||115 oz / 3,3 L|
|240 lb / 108,9 kg||120 oz / 3,4 L|
|250 lb / 113,4 kg||125 oz / 3,5 L|
|260 lb / 117,9 kg||130 oz / 3,7 L|
|270 lb / 122,5 kg||135 oz / 3,8 L|
|280 lb / 127,0 kg||140 oz / 4,0 L|
WHEN YOU NEED MORE WATER
You might need more water than other people of your age and weight. How much water you need also depends on the following factors:
- Where you live. You will need more water in hot, humid, or dry areas. You’ll also need more water if you live in the mountains or at a high altitude.
- Your diet. If you drink a lot of coffee and other caffeinated beverages you might lose more water through extra urination. You will likely also need to drink more water if your diet is high in salty, spicy, or sugary foods. Or, more water is necessary if you don’t eat a lot of hydrating foods that are high in water like fresh or cooked fruits and vegetables.
- The temperature or season. You may need more water in warmer months than cooler ones due to perspiration.
- Your environment. If you spend more time outdoors in the sun or hot temperatures or in a heated room, you might feel thirstier faster.
- How active you are. If you are active during the day or walk or stand a lot, you’ll need more water than someone who’s sitting at a desk. If you exercise or do any intense activity, you will need to drink more to cover water loss.
- Your health. If you have an infection or a fever, or if you lose fluids through vomiting or diarrhea, you will need to drink more water. If you have a health condition like diabetes you will also need more water. Some medications like diuretics can also make you lose water.
- Pregnant or breastfeeding. If you’re pregnant or nursing your baby, you’ll need to drink extra water to stay hydrated. Your body is doing the work for two (or more), after all.
HOW TO KNOW IF YOU’RE DRINKING ENOUGH WATER
No formula needed for this one: To check if you’re hydrated, take a quick look at your urine. If it’s pale yellow, you’re probably drinking enough water. On the other hand, a dark yellow color could be a sign that you need to amp up your hydration.
Just bear in mind that urine color isn’t a perfect indicator. A darker color can also result from certain health conditions, medications, vitamin B2 supplements, and natural pigments in certain foods.
Other common signs of dehydration
That’s why it’s helpful to be on the lookout for other signs that your water intake might be too low. Dehydration can also be marked by:
- Feeling thirsty
- Dry mouth
- Difficulty concentrating
- Dry skin
Dehydration can make you feel ill and, if not treated properly and quickly, can sometimes even be life-threating.
Dehydration is associated with kidney stones. Otherwise, there’s little evidence linking dehydration with chronic disease. Occasional bouts of mild dehydration are common.
WHAT IF TOO MUCH …
Drinking too much water is rarely a problem for healthy, well-nourished adults. Athletes occasionally may drink too much water in an attempt to prevent dehydration during long or intense exercise.
When you drink too much water, your kidneys can’t get rid of the excess water. The sodium content of your blood becomes diluted. This is called hyponatremia and it can be life-threatening.
- Foods and fluids, including water, are the main source of water in our bodies.
- The advice to drink eight 8-ounce glasses of water a day is not based on evidence.
- The amount of water we need depends on individual needs and circumstances, including activity and climate.
- The healthy body naturally maintains a well-tuned balance of fluid, and the thirst mechanism tells us when we need more.