Water is essential for life. It makes up over half of the human body and is vital for many bodily functions including digestion, metabolism, circulation, creating saliva, transportation of nutrients, maintenance of body temperature, and kidney and brain function. With water playing such a crucial role, how much H2O should you aim to drink each day? Here’s a deeper look into the recommended daily water intake.
Quick Answers
The basic daily water intake recommendations are:
- Men: 15.5 cups (3.7 liters)
- Women: 11.5 cups (2.7 liters)
However, water needs can vary based on factors like age, activity level, health conditions, pregnancy/lactation status, and climate.
How Much Water Do You Need Based on Age and Gender?
Water needs differ based on age and biological sex. Here are the recommendations by life stage:
Infants & Toddlers
- 0-6 months: 1.5-2.5 cups (350-600 ml) total from breastmilk or formula
- 6-12 months: 2-3 cups (470-710 ml) total from breastmilk, formula, water and foods
- 1-2 years: 2.5-5 cups (590-1,180 ml)
Children
- 2-3 years: 3.5-5 cups (830-1,180 ml)
- 4-8 years: 5 cups (1,200 ml)
Boys
- 9-13 years: 8-10 cups (1,900-2,400 ml)
- 14-18 years: 11-15.5 cups (2,600-3,700 ml)
Girls
- 9-13 years: 7-10 cups (1,600-2,400 ml)
- 14-18 years: 8.5-11.5 cups (2,000-2,700 ml)
Adult Men
- 19+ years: 15.5 cups (3.7 liters)
Adult Women
- 19+ years: 11.5 cups (2.7 liters)
Pregnant Women
- 14-18 cups (3.3-4.3 liters)
Lactating Women
- 16-19 cups (3.8-4.5 liters)
Adjusting Your Water Intake
While the recommendations above provide a good starting point, your personal water needs can vary based on your health, activity level, and climate:
Activity Level
If you are very active, sweat a lot or exercise for over an hour daily, you may need more water. Add 12 ounces (350 ml) of water for every 30 minutes of exercise.
Hot Climates
In hot and humid weather, you’ll need more water to replace what you lose through sweat. Add another 2-4 cups (470-950 ml) when it’s hot.
High Altitudes
The air is drier at higher altitudes, so your water needs increase. Have an extra 3-4 cups (710-950 ml) per day if at altitudes over 8,200 feet (2,500 meters).
Illnesses
Sicknesses like diarrhea, vomiting, fever and infections increase water loss. Drink extra and follow your doctor’s hydration advice when ill.
Health Conditions
Underlying conditions like diabetes, heart and kidney disease can also increase your fluid needs.
Breastfeeding
Breastfeeding mothers need to stay well hydrated to produce enough milk. Have 16-19 cups (3.8-4.5 liters) daily.
Signs of Dehydration
Some signs that your water intake may be inadequate include:
- Dry mouth
- Cramping during exercise
- Headache
- Dizziness
- Fatigue
- Dark urine
- Rapid heartbeat
- Constipation
Severe dehydration can cause serious complications like brain swelling, kidney failure, seizures, coma or even death. Watch for signs of not drinking enough water.
Tips for Staying Hydrated
Strategies for optimizing your water intake include:
- Carry a water bottle – Having water with you at all times makes sipping easier.
- Drink before feeling thirsty – Don’t rely on thirst to know when to drink, as you may already be dehydrated by then.
- Set reminders – Use your phone, smart watch or an app to prompt you to drink up.
- Choose water most often – Limit sugary drinks and opt for plain or sparkling water.
- Eat water-rich foods – Things like fruits, veggies and brothy soups add fluids.
- Avoid excess alcohol and caffeine – These have a diuretic effect.
- Track your intake – Note how much you drink to ensure you hit your goal.
Water vs Other Beverages
Plain water is ideal for meeting your fluid needs. Other beverages can contribute to your daily total, but may have downsides:
Milk
Milk provides fluids, calcium, vitamin D, protein and other nutrients. But it contains calories, lactose and casein protein – which some people don’t tolerate well.
Juice
100% fruit juice counts towards your fluid intake, but is high in natural sugars. Limit to a small glass per day.
Coffee & Tea
These provide hydration, but their caffeine content has a mild diuretic effect if consumed in excess.
Soda & Sweet Drinks
Beverages like soda, lemonade and sweet iced tea are very high in added sugar and provide little nutritional value.
Alcohol
Alcohol acts as a diuretic, causing you to urinate more and get dehydrated. Drink a glass of water with each alcoholic beverage.
The Takeaway
Stick with water as your primary beverage and drink other liquids in moderation to meet your daily fluid needs.
How Much Water Do You Need Based on Weight?
A simple way to estimate your water needs is to take your weight in pounds and divide that number in half. That gives you the number of ounces of water to aim for each day.
For example, if you weigh 150 pounds, you would need 75 ounces or about 9 cups of water per day (150/2 = 75).
This calculation provides a ballpark estimate, but your individual hydration needs may be higher or lower based on activity, climate, health status and other factors.
Water Intake Recommendations By Organization
A number of major health organizations have provided general daily water intake recommendations. Here’s a look at the specific guidelines from different groups:
| Organization | Recommendations |
|---|---|
| Institute of Medicine (IOM) | Women: 11.5 cups (2.7 liters) Men: 15.5 cups (3.7 liters) |
| European Food Safety Authority (EFSA) | Women: 9 cups (2.0 liters) Men: 13 cups (3.0 liters) |
| National Academies of Sciences, Engineering, and Medicine | Women: 11.5 cups (2.7 liters) Men: 15.5 cups (3.7 liters) |
| Mayo Clinic | Women: 11.5 cups (2.7 liters) Men: 15.5 cups (3.7 liters) |
As you can see, the recommendations are fairly consistent across groups, with adult men needing about 15.5 cups (3.7 liters) and women needing about 11.5 cups (2.7 liters) daily. This equals about 125 ounces (3.7 liters) for men and 91 ounces (2.7 liters) for women.
Does Caffeine Dehydrate You?
Caffeine has a mild diuretic effect, meaning it causes increased urination and fluid loss. However, research shows this effect is smaller than commonly believed and doesn’t offset caffeine’s fluid-contributing properties.
In a review of 18 studies, caffeine intakes of up to 6 mg per kg body weight (about 440 mg) did not lead to dehydration or total body water loss in most situations.
So while caffeinated beverages cause a modest increase in urine output, they still count toward your daily fluid needs. Those who consume caffeine daily build up a tolerance to its diuretic effects.
Tips for Caffeine & Hydration
- Limit caffeine to 400 mg or less to minimize fluid loss.
- Spread consumption throughout the day rather than a few large doses.
- Have a glass of water with each caffeinated drink.
- Avoid caffeine a few hours before activities causing heavy sweating.
As long as you drink enough non-caffeinated fluids and account for the mild effects of caffeine, it doesn’t dehydrate you.
Does Alcohol Dehydrate You?
Alcohol acts as a diuretic, causing increased urination and fluid loss. Studies show alcohol increases urine output by about 10 ml for every gram of alcohol consumed.
This diuretic effect combined with vomiting from intoxication can lead to dehydration. Hangovers are largely caused by alcohol’s dehydrating effects.
To prevent dehydration, aim to alternate each alcoholic drink with a glass of water. Avoid excessive alcohol intake and monitor your hydration status when drinking.
Meeting Your Fluid Needs
Getting adequate water each day is vital for health, from your heart to your muscles to your brain. Make hydration a priority by:
- Sipping water consistently throughout the day
- Drinking before, during and after exercise
- Eating water-rich fruits and vegetables
- Carrying a water bottle for easy access
- Choosing water over sugary drinks
- Listening to your thirst cues
- Monitoring urine color
- Tracking your daily intake
- Adjusting for individual hydration needs
Meeting your individualized fluid needs will keep all systems running smoothly.
The Bottom Line
How much water you need daily depends on factors like age, gender, activity level, climate and health status. The basic recommendations are 15.5 cups (3.7 liters) for men and 11.5 cups (2.7 liters) for women.
But monitor your own hydration indicators and tweak your water intake to meet your personal needs for optimal health.
