Pediatric Fluid Requirements Calculator
Calculates a child's daily fluid requirement in milliliters using the Holliday-Segar method, adjusted for activity level and clinical conditions like fever or dehydration. Ideal for parents, nurses, and pediatric caregivers.
Last updated: October 2026
Daily Fluid Requirements
1,500 ml/day
Formula below · 3 sources (pubmed.ncbi.nlm.nih.gov, ncbi.nlm.nih.gov, CDC) · Updated Oct 2026
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About this calculator
A healthy 20 kg child needs about 1,500 mL of fluid a day by the Holliday–Segar method: 100 mL/kg for the first 10 kg plus 50 mL/kg for the next 10. For children over 20 kg add 20 mL/kg for each extra kilogram. This calculator starts from that maintenance volume and adjusts it for activity, fever, fluid restriction or mild dehydration.
The adjustments
The base volume is multiplied by 0.9 for low activity, 1.0 for normal activity or 1.2 for high activity and sports, then by 1.15 for fever or 0.8 when a clinician has restricted fluids. For mild dehydration, the deficit is added on top: about 50 mL per kg, in line with oral rehydration plans for mild dehydration. These factors are planning approximations, not measured requirements.
Food counts too
Holliday–Segar estimates total water need, and part of a child's water comes from food. The National Academies' adequate intakes for total water from all drinks and foods are 1.3 liters a day for ages 1 to 3, 1.7 liters for ages 4 to 8, and 2.4 liters for boys and 2.1 liters for girls aged 9 to 13 (see the table below). A child who is active, urinating normally and producing pale urine is usually drinking enough.
When to call a doctor
Seek care for signs of dehydration such as very little urine, a dry mouth, no tears, sunken eyes, unusual sleepiness, or vomiting that prevents drinking. Mild dehydration is treated with oral rehydration solution rather than plain water; severe dehydration needs emergency care.
| Age group | Total water per day |
|---|---|
| Children 1–3 years | 1.3 L |
| Children 4–8 years | 1.7 L |
| Boys 9–13 years | 2.4 L |
| Girls 9–13 years | 2.1 L |
How to use
Enter the child's weight in kg, then choose the activity level and any clinical condition. The default, a 20 kg child with normal activity and no illness, gives 1,500 mL a day. A 15 kg child with a fever and normal activity gives 1,250 × 1.15 ≈ 1,438 mL. With mild dehydration selected, 50 mL per kg is added to maintenance: 1,500 + 1,000 = 2,500 mL for a 20 kg child.
Frequently asked questions
How much fluid does a child need per day by weight?
By the Holliday–Segar method: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg for each kg above 20. That is 1,000 mL for a 10 kg child, 1,500 mL for 20 kg and 1,600 mL for 25 kg. This is total water, including water in food.
How much water should children drink according to dietary guidelines?
The National Academies set adequate intakes for total water, from drinks and food combined, of 1.3 L a day for ages 1 to 3, 1.7 L for ages 4 to 8, 2.4 L for boys 9 to 13 and 2.1 L for girls 9 to 13. Needs rise in hot weather and with exercise.
Why does fever increase fluid needs?
Fever raises metabolic rate and increases water lost through the skin and breathing. This calculator adds 15% for fever as a planning allowance. Offer fluids often, and seek medical advice if the child cannot keep fluids down or shows signs of dehydration.
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Sources & references
- Holliday MA, Segar WE (1957). The maintenance need for water in parenteral fluid therapy. Pediatrics 19:823–832 (PubMed)
- National Academies — Dietary Reference Intakes summary tables: total water (NCBI Bookshelf)
- CDC, MMWR Recommendations and Reports (2003) — Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy
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