People often hear that they should drink eight glasses of water per day. However, the amount of water a person should drink can vary depending on their age, activity level, and more.
The commonly touted wisdom of eight glasses of water per day may be suitable for some people, but it is not a “one-size-fits-all” recommendation.
Some experts say there is a lack of scientific evidence supporting these claims.
A note about sex and gender
Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Learn more.
Back in 1945, the U.S. Food and Nutrition Board advised people to consume 2.5 liters, or 84.5 fluid ounces (fl oz), of water per day, including fluid from prepared foods. Today, the Centers for Disease Control and Prevention (CDC) says there is
The
In the United Kingdom, the National Health Service (NHS) recommends consuming 6–8 glasses of fluids a day, or 1.9 liters (almost 65 fl oz), including water in food, water, milk, low sugar or sugar-free drinks, and tea or coffee. The NHS notes this amount is suitable for a temperate climate, more will be needed in hotter climates.
Learn about the benefits of drinking water.
There is no fixed amount of fluid recommended by age, but some patterns emerge among healthy individuals doing a moderate amount of activity in a temperate climate.
The following sections show the average water intake for people of different ages.
Infants
Experts do not recommend plain water for infants before the
If infants over 6 months of age need additional fluid on hot days, they can consume small amounts of water in a bottle. However, their primary form of fluid and calories should be human milk or formula.
Children over 12 months of age
It is important to encourage children over 12 months of age to drink water regularly. Water can help keep bowel movements regular and help prevent urinary tract infections (UTIs) and kidney stones.
Keeping hydrated can also help the body to regulate its temperature.
The Children’s Hospital of Orange County (CHOC) recommends that children drink the same amount of 8-ounce glasses of water each day as their age. For example, a 1-year-old should drink 1 glass. CHOC also notes that certain types of drinks should be limited as they can discourage children from drinking water. These include fruit juices, soda, flavored milk, and drinks with added sugars.
They recommend that water, plain milk, and milk alternatives should be a staple part of a child’s diet.
Adults age 19 to 30 years
The recommended adequate intakes of total water from all sources each day for most adults between 19 and 30 years of age are:
- Males: 3,700 milliliters (130 ounces) per day
- Females: 2,700 ml (95 oz) per day
People who are pregnant or nursing may require a higher water intake.
A note on water intake
It is important to remember that these are recommendations. Various factors, such as weight, lifestyle, and activity level can influence how much water a person needs to drink.
For example, a person who participates in vigorous activity will typically require more water than someone who does not.
These values also represent total water intake. This includes plain water, other beverages, and moisture gained from food.
Older adults
Older adults may be at a higher risk of dehydration, especially those who have multiple chronic conditions.
Dehydration in older adults can lead to:
- increase of metabolic diseases
- increase of renal diseases, such as kidney disease
- affects on cognitive functioning
Various international medical organizations recommend the following fluid intakes for individuals over the age of 50 years old:
- Males: 1.7 to 3 liters (60 to 106 oz)
- Females: 1.5 to 2.2 liters (53 to 77 oz)
Weight can be one of the variables for how much water a person should drink. An equation that can help a person figure out how much water they should possibly be drinking based on their weight is:
weight x 0.5 = oz of water per day
For example:
200lbs x 0.5 = 100 oz per day
Basically, a person should drink, in ounces, half their body weight each day.
This can vary based on how much physical activity a person does or is doing at a particular time.
People can consume water by:
- drinking water and other fluids
- eating foods high in water, such as fruits and vegetables
While drinking water is important, people get at least part of their fluid intake from the foods they eat. A higher intake of fresh fruit and vegetables generally means a higher intake of water from foods.
Here are some examples of the
| Water content as a percentage (%) | Food or drink |
|---|---|
| 100% | water |
| 90 to 99% | •fat-free milk •juicy fruits, such as strawberries, watermelon, and cantaloupe •vegetables, such as lettuce, celery, spinach, cabbage, and squash |
| 80 to 89% | •fruit juice •yogurt •fruits. such as apples, grapes, pineapple, and oranges •vegetables, such as carrots and broccoli |
| 70 to 79% | •bananas •avocados •baked potatoes •cottage cheese •ricotta cheese •shrimp |
| 60 to 69% | •pasta •legumes, such as beans and peas •fish, such as salmon •chicken breasts |
| 30 to 39% | •bread •bagels •cheddar cheese |
| 20 to 29% | •cake •biscuits •pepperoni |
| 10 to 19% | •raisins •butter •margarine |
| 1 to 9% | •nuts, such as walnuts and dry-roasted peanuts •crackers •cereals •pretzels •peanut butter |
| 0% | •oils •sugars |
During exercise, people may need to consume more water than usual. The amount they should drink depends on:
- the type and intensity of the activity
- environmental factors, such as temperature
- the size and muscle mass of the individual
Government recommendations state that during a workout individuals should drink 8 to 12 oz of water every 15 minutes. However, drinking more than 1.5 liters in an hour is not recommended.
During higher temperatures, the intake of water may require adjustment.
The recommendations are to weigh oneself before a workout and then again afterward. Then a person can drink 16 to 24 oz of water for every pound they lose during exercise.
The important thing to remember is to stay hydrated when exercising or participating in physical activity, especially in higher temperatures.
If a person drinks too much water, such as more than 1.5 liters in an hour, it could lead to hyponatremia, which is when sodium levels in the blood plasma become too low.
Symptoms of hyponatremia include:
- nausea and vomiting
- muscle spasms, weakness, or cramping
- dizziness when standing
- low blood pressure
- loss of appetite
- fatigue or low-energy
- short temper
- restlessness
Serious symptoms that can occur in severe cases include:
- decreased consciousness
- altered mental state, such as confusion
- seizures
- hallucinations
- coma
Hyponatremia usually affects endurance athletes, people with diabetes, and those taking certain medications.
The amount of water a person needs varies based on their age, size, activities, and climate.
Although many still choose to follow the eight 8 oz glass of water per day rule, it may be outdated and overly simplistic. The body is incredibly good at maintaining its water balance, and it urges people to drink more by making them thirsty.
People who work outdoors in hot climates or exercise vigorously may need to consume more water. They can also get fluid from foods high in water, such as fruits and vegetables.
