What is the 4-2-1 rule?

4 mL/kg for the first 10kg, 2 mL/kg for the next 10kg, and 1 mL/kg for any remaining weight.

Pediatric Maintenance Fluids – 4-2-1 Hydration Service | CalcTools

Calculate hourly and daily fluid requirements for children. Pediatric hydration service.

Children are highly sensitive to fluid balance, and their hydration needs are not simply a fraction of an adult's. They require a tiered approach that accounts for their higher metabolic rate relative to their size. Our Pediatric Hydration service uses the standard '4-2-1 rule' (Holliday-Segar method) to provide both the hourly pump rate and the total 24-hour volume required. This is an essential safety service for clinicians managing hospitalized children who cannot take fluids by mouth.

Educational use only. This tool does not replace clinical judgment or local protocols.

Child Weight (kg)

Formula

Hourly Rate (mL/hr)

50 mL/hr

Maintenance fluids: 50 mL/hr (1200 mL/day)

40 mL + 2 mL/kg/hr * (15 - 10) kg

Child Weight (kg)15 kg

Daily Total (mL/day)1200 mL/day

Method4-2-1 Rule

How it Works

The tool applies three mathematical tiers based on the child's weight, ensuring that smaller infants get more fluid per kilogram than teenagers, accurately reflecting their caloric and water needs.

Calculation Formula

Tiered: 4ml/kg + 2ml/kg + 1ml/kg

Calculation Examples

1. **25kg Child**: (10*4)+(10*2)+(5*1) = **65 mL/hr**.

Why use this tool in your daily life?

This service ensures hydration safety for the most vulnerable patients. By automating the tiered calculation, it eliminates the risk of dehydration or fluid overload in pediatric care, making it an indispensable tool for pediatric nurses and residents.