Pediatric Fluid Replacement Calculator
Estimates the hourly oral or IV fluid replacement rate for a dehydrated child based on weight, dehydration severity, ongoing losses, and the desired replacement timeframe. Use it when managing gastroenteritis or other causes of childhood dehydration.
About this calculator
Pediatric fluid replacement follows a deficit-plus-ongoing-losses model. The deficit volume in mL is estimated as weight (kg) × a severity factor: 50 mL/kg for mild dehydration (~5%), 100 mL/kg for moderate (~10%), and 150 mL/kg for severe (~15%). Ongoing losses — from continued vomiting or diarrhea — add an additional 10 mL/kg for mild losses or 20 mL/kg for significant losses. The combined volume is divided by the planned replacement hours to give an hourly infusion or oral rehydration rate. Formula: rate (mL/hr) = round((weight × dehydrationFactor + weight × ongoingLossFactor) / replacementHours). This is a clinical estimation tool; actual fluid therapy should always be supervised by a healthcare provider who can monitor the child's response.
How to use
A 12 kg child presents with moderate dehydration (factor = 100 mL/kg) and significant ongoing losses (factor = 20 mL/kg). Replacement is planned over 8 hours. Deficit volume = 12 × 100 = 1200 mL. Ongoing loss volume = 12 × 20 = 240 mL. Total = 1440 mL. Hourly rate = 1440 / 8 = 180 mL/hr. For mild dehydration with no ongoing losses over 4 hours: (12 × 50 + 0) / 4 = 150 mL/hr.
Frequently asked questions
How do you assess the severity of dehydration in a child?
Mild dehydration (around 5% body weight loss) typically shows increased thirst, slightly dry mouth, and decreased urine output. Moderate dehydration (around 10%) adds sunken eyes, reduced skin turgor, and a dry tongue. Severe dehydration (around 15%) involves lethargy, markedly sunken fontanelle in infants, very dry mucous membranes, and minimal or no urine for many hours. Clinical assessment by a healthcare professional is essential, especially for moderate and severe cases.
What fluids are recommended for oral rehydration in children with diarrhea?
The WHO and UNICEF recommend low-osmolarity oral rehydration solution (ORS) — a precise mix of sodium, potassium, glucose, and water — as the first-line treatment for mild-to-moderate dehydration from diarrhea. Plain water, sports drinks, and soft drinks are not appropriate substitutes because they lack the correct electrolyte balance and can worsen the condition. ORS sachets are widely available at pharmacies and should be mixed exactly as directed.
When does a dehydrated child need intravenous fluids instead of oral rehydration?
IV fluids are indicated when a child cannot tolerate oral intake due to persistent vomiting, when dehydration is severe (≥10% body weight loss), when the child shows signs of shock such as rapid weak pulse or altered consciousness, or when there is a clinical concern that oral therapy is failing. In these situations, emergency medical care should be sought immediately. Mild-to-moderate dehydration without vomiting can usually be managed safely at home with ORS given in small, frequent amounts.