Proper hydration is essential for people of all ages. Water needs vary significantly throughout life, from infancy to old age, and are influenced by factors like body size, activity level, and biological sex. This comprehensive guide provides evidence-based recommendations for daily water intake by age.
The chart below shows the recommended daily fluid intake by age and sex, based on guidelines from the Australian National Health and Medical Research Council (NHMRC) and the New Zealand Ministry of Health.
Daily Water Intake Recommendations by Age and Sex
Water Intake Chart
| Age | Sex | Fluids* | Visual Guide |
|---|---|---|---|
| 1-3 years | All | 1.0 L/day | |
| 4-8 years | All | 1.2 L/day | |
| 9-13 years | Boys | 1.6 L/day | |
| 9-13 years | Girls | 1.4 L/day | |
| 14-18 years | Boys | 1.9 L/day | |
| 14-18 years | Girls | 1.6 L/day | |
| 19+ years | Men | 2.6 L/day | |
| 19+ years | Women | 2.1 L/day |
* Including plain water, milk, and other drinks
Source: Extracted from The Nutrient Reference Values (NRVs), a joint initiative of the Australian National Health and Medical Research Council (NHMRC) and the New Zealand Ministry of Health (MoH)
Important Note
Understanding Water Needs by Age Group
Young Children (1-8 years)
Children have higher water requirements relative to their body weight compared to adults. Their bodies contain a higher percentage of water, and they have:
- Higher metabolic rates and greater surface area relative to their mass
- Less developed thirst mechanisms, making them more vulnerable to dehydration
- Different kidney function that limits their ability to concentrate urine
Recommended daily intake:
Ages 1-3: 1.0 liter (about 4 cups)
Ages 4-8: 1.2 liters (about 5 cups)
Adolescents (9-18 years)
During adolescence, water needs increase significantly due to:
- Rapid growth and development
- Hormonal changes affecting fluid balance
- Increased physical activity (especially in sports)
- Greater body surface area and sweat production
Gender differences become apparent during this stage, with boys typically requiring more water than girls due to greater muscle mass and different hormonal profiles.
Recommended daily intake:
Boys 9-13: 1.6 liters (about 6+ cups)
Girls 9-13: 1.4 liters (about 5.5+ cups)
Boys 14-18: 1.9 liters (about 7.5+ cups)
Girls 14-18: 1.6 liters (about 6+ cups)
Adults (19+ years)
Adult water requirements stabilize but remain different between men and women due to:
- Differences in average body composition (men typically have more muscle mass)
- Metabolic rate variations
- Hormonal differences affecting fluid retention
Special circumstances like pregnancy, breastfeeding, intense physical activity, or certain medical conditions may increase water needs beyond these baseline recommendations.
Recommended daily intake:
Men: 2.6 liters (about 10+ cups)
Women: 2.1 liters (about 8+ cups)
Factors That Affect Water Needs Beyond Age
While age and sex provide baseline recommendations, several other factors can significantly influence individual hydration requirements:
Physical Activity
Exercise increases water loss through sweat. Add 400-800ml per hour of moderate activity.
Climate
Hot or humid environments increase fluid needs by 500-1000ml daily due to increased sweating.
Other important factors include:
- Health conditions: Fever, vomiting, diarrhea, and certain chronic conditions can increase fluid needs
- Pregnancy and breastfeeding: Women need approximately 700-1000ml additional water daily
- Diet: High protein or high sodium diets may increase water requirements
- Medications: Some medications act as diuretics, increasing fluid loss
Signs of Dehydration by Age Group
Recognizing dehydration symptoms is crucial, as they can vary by age:
| Age Group | Common Signs of Dehydration |
|---|---|
| Young Children (1-8 years) |
|
| Adolescents (9-18 years) |
|
| Adults (19+ years) |
|
Important Warning
Frequently Asked Questions About Water Intake by Age
Is the 8x8 rule (eight 8-ounce glasses) accurate for everyone?
The popular "8x8 rule" recommends about 1.9 liters daily, which is close to the needs of teenage girls and adult women, but may be insufficient for adult men and too much for young children. Age-specific recommendations are more accurate than this one-size-fits-all approach.
Do children need to drink water even when they're not thirsty?
Yes. Children's thirst mechanisms are less developed than adults', and they may not recognize thirst signals until they're already mildly dehydrated. Regular water breaks throughout the day are recommended, especially during physical activity and hot weather.
Do older adults need less water?
While the base recommendations don't change for adults over 65, older adults often have a diminished sense of thirst and may be at higher risk of dehydration. Some may need to consciously drink water throughout the day even when not feeling thirsty. Certain medications common in older adults may also increase fluid needs.
Do juice, milk, coffee, and tea count toward daily water intake?
Yes, all beverages contribute to hydration. The recommendations in the chart include fluid from all drinks. However, water is still the healthiest choice for most of your fluid needs as it contains no calories, sugar, or additives. Caffeinated beverages have a mild diuretic effect but still provide net hydration.
Calculate Your Personalized Water Intake
While age and sex provide a good baseline, your exact water needs depend on many individual factors. Use our calculator to get a personalized recommendation based on your weight, activity level, and environment.
Calculate Your Personal Water Needs
Get a precise water intake recommendation based on your exact weight, activity level, and environment.
Related Water Intake Guides
Explore our other detailed hydration guides:
Hydration Tips for All Ages
Start the day with a glass of water to rehydrate after sleep
Carry a reusable water bottle to encourage regular sipping
Set reminders to drink water throughout the day
Eat water-rich foods like fruits and vegetables
Drink extra water before, during, and after exercise