How Much Water Should a Baby Drink?
Under 6 months, infants need no plain water at all — breast milk or formula supplies everything. Once solids begin, small amounts of water are introduced, with intake rising steadily through the first years of life.
Quick answer
How Much Water Should a Baby Drink?
Babies under 6 months should not drink plain water — breast milk or formula supplies all their fluid, expressed by EFSA's 2010 Dietary Reference Values as 100-190 mL/kg/day of total water from milk. From 6-12 months, once solids begin, EFSA sets a total-water Adequate Intake of 800-1000 mL/day from food plus all beverages. Always confirm with your pediatrician.
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For roughly the first 6 months of life, healthy babies should not be given plain water: breast milk or infant formula supplies all the fluid they need, and added water can dilute electrolytes and displace nutrition. EFSA's 2010 Dietary Reference Values do not assign a plain-water target for this window; instead they describe total water (from milk feeds) at 100-190 mL/kg/day in the first half of the first year. From 6-12 months, as solids are introduced, EFSA sets a total-water Adequate Intake of 800-1000 mL/day from all sources, rising to 1100-1200 mL/day in the second year of life. For clinical estimates of a child's daily fluid needs by body weight, pediatricians use the Holliday-Segar maintenance formula: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg for each kilogram above 20 kg. This page summarizes published reference figures and is not a substitute for advice from your pediatrician.
Infant & Toddler Fluid Reference (EFSA Total-Water AI)
| Age | Recommended intake | Notes |
|---|---|---|
| 0-6 months | No plain water Breast milk or infant formula only. EFSA expresses total water in this window as 100-190 mL/kg/day, all supplied by milk feeds — not as added plain water. | |
| 6-12 months | 800-1000 mL/day total water Once complementary foods (solids) begin, small amounts of plain water can be offered. The EFSA total-water Adequate Intake covers water from food plus all beverages. | |
| Second year (1-2 y) | 1100-1200 mL/day total water Total-water Adequate Intake from food plus beverages under moderate temperature and activity. | |
| 2-3 years | 1300 mL/day total water EFSA Adequate Intake, boys and girls, including water from food plus all beverages. |
Holliday-Segar Maintenance Fluid Formula (by body weight)
| Body weight | Daily fluid | Hourly equivalent |
|---|---|---|
| First 10 kg | 100 mL/kg/day 4 mL/kg/hr (the '4' of the 4-2-1 rule). | |
| Second 10 kg (10-20 kg) | 50 mL/kg/day 2 mL/kg/hr (the '2' of the 4-2-1 rule). | |
| Each kg above 20 kg | 20 mL/kg/day 1 mL/kg/hr (the '1' of the 4-2-1 rule). |
Why Babies Under 6 Months Shouldn't Drink Plain Water
Milk Already Supplies the Water
EFSA expresses an infant's total water in the first half of the first year as 100-190 mL/kg/day — all of it delivered through breast milk or formula, not as separate plain water (EFSA 2010 Water DRV).
Plain Water Can Be Harmful
Giving plain water to a young infant can displace nutritious milk and risks diluting body electrolytes. Because EFSA assigns no plain-water target before 6 months, the safest approach is milk feeds only until solids begin.
Solids Are the Turning Point
Once complementary foods start around 6 months, EFSA sets a total-water Adequate Intake of 800-1000 mL/day from all sources, so small sips of water alongside meals become appropriate (EFSA 2010 Water DRV).
Estimating Needs by Weight
For a clinical estimate, the Holliday-Segar formula gives 100 mL/kg/day for the first 10 kg of body weight — so a 7 kg baby's calculated maintenance is about 700 mL/day (Holliday-Segar 1957).
Practical Tips for Baby Hydration
- Under 6 months: offer breast milk or formula only — no plain water, juice, or other drinks unless your pediatrician advises otherwise
- From about 6 months, when solids begin, you can offer small amounts of plain water in an open or sippy cup with meals
- Use EFSA's total-water figures (800-1000 mL/day at 6-12 months) as totals from food plus all beverages, not as plain-water-only targets
- To estimate a child's daily maintenance fluid, apply Holliday-Segar: 100 mL/kg for the first 10 kg, then 50 mL/kg for 10-20 kg, then 20 mL/kg above 20 kg
- Watch for dehydration signs such as fewer wet diapers, no tears when crying, or a dry mouth, and contact your pediatrician promptly
- Needs rise in hot weather, with fever, or during diarrhea/vomiting — ask your pediatrician about oral rehydration in those cases
Medical Disclaimer: This page summarizes published reference values (EFSA 2010 Dietary Reference Values and the Holliday-Segar 1957 maintenance formula) for general education only. It is not medical advice. Infant feeding and hydration decisions — especially giving any plain water before 6 months — should follow the guidance of your pediatrician or a qualified health professional.
Estimate Daily Fluid Needs by Weight
Use our calculator to apply weight-based reference figures and get a quick daily fluid estimate for older children and adults.
Open the Hydration CalculatorSources & Citations
- 100-190 mL/kg/day — In the first half of the first year, EFSA expresses an infant's total water as 100-190 mL/kg/day, supplied by breast milk or formula — not as added plain water.[1]
- 800-1000 mL/day — EFSA total-water Adequate Intake for infants 6-12 months (water from food plus all beverages).[1]
- 1100-1200 mL/day — EFSA total-water Adequate Intake in the second year of life (1-2 years).[1]
- 1300 mL/day — EFSA total-water Adequate Intake for children aged 2-3 years, boys and girls.[2]
- 100 mL/kg/day — Holliday-Segar maintenance fluid for the first 10 kg of body weight (4 mL/kg/hr).[3]
- 50 mL/kg/day — Holliday-Segar maintenance fluid for the second 10 kg of body weight, 10-20 kg (2 mL/kg/hr).[3]
- 20 mL/kg/day — Holliday-Segar maintenance fluid for each kilogram above 20 kg (1 mL/kg/hr).[3]
- [1]EFSA 2010 Water DRV — EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). Scientific Opinion on Dietary Reference Values for water. EFSA Journal. 2010;8(3):1459.DOI: 10.2903/j.efsa.2010.1459
- [2]EFSA DRV Summary Table — EFSA. Summary of Dietary Reference Values — overview table (Adequate Intakes for water, L/day, by age and sex). European Food Safety Authority, January 2017.
- [3]Holliday-Segar 1957 — Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832.DOI: 10.1542/peds.19.5.823
Last reviewed: 2026-06-20. Every figure on this page is sourced to the named primary references above.
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Frequently Asked Questions
Can babies drink water under 6 months old?
No. Healthy babies under 6 months should not be given plain water — breast milk or infant formula supplies all the fluid they need. EFSA's 2010 Dietary Reference Values express an infant's total water in the first half of the first year as 100-190 mL/kg/day, all delivered through milk feeds, and assign no separate plain-water target. Added water can dilute electrolytes and displace nutrition, so check with your pediatrician first.
How much water should a 6-12 month old baby have?
Once complementary foods (solids) are introduced around 6 months, EFSA's 2010 Dietary Reference Values set a total-water Adequate Intake of 800-1000 mL/day for infants aged 6-12 months. Importantly, that figure covers water from food plus all beverages, not plain water alone. Small amounts of plain water can be offered alongside meals during this stage.
How much water does a 1 to 2 year old need?
EFSA's 2010 reference values set a total-water Adequate Intake of 1100-1200 mL/day in the second year of life (1-2 years), rising to 1300 mL/day at 2-3 years per the EFSA DRV Summary Table. These totals include water from food as well as all beverages, assuming moderate temperature and physical activity.
How do I calculate how much fluid my baby or child needs?
Pediatricians use the Holliday-Segar maintenance formula (Pediatrics, 1957): 100 mL/kg of body weight for the first 10 kg, plus 50 mL/kg for the next 10 kg (10-20 kg), plus 20 mL/kg for each kilogram above 20 kg. For example, an 8 kg baby's estimated maintenance is about 800 mL/day. The hourly '4-2-1' rule (4, 2, 1 mL/kg/hr) is the equivalent.
Why can't newborns have plain water?
A newborn's kidneys and electrolyte balance are still developing, and plain water can dilute the sodium in their blood while displacing nutritious milk. EFSA's 2010 Dietary Reference Values describe infant total water in the first half of the first year as 100-190 mL/kg/day supplied entirely by breast milk or formula, with no plain-water allowance. Always follow your pediatrician's guidance.
Do formula-fed babies need extra water?
Correctly prepared infant formula already contains the water a young baby needs, so under 6 months no extra plain water is required. EFSA's total water for this window — 100-190 mL/kg/day — is met by formula or breast milk alone. Never dilute formula with extra water to stretch it, and ask your pediatrician before offering any plain water.
How much water should a 2 to 3 year old toddler drink?
Per EFSA's 2010 Dietary Reference Values (DRV Summary Table), the total-water Adequate Intake for children aged 2-3 years is 1300 mL/day for both boys and girls. This total includes water from food plus all beverages, under moderate temperature and activity, so the plain-water portion is smaller than the full figure.
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