What is the Holliday-Segar formula?

The Holliday-Segar formula — also called the 4-2-1 rule — was published in 1957. It estimates pediatric maintenance fluid needs as 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, and 20 mL/kg/day for each kilogram above 20 kg. The 4-2-1 shorthand describes the equivalent hourly rates: 4 mL/kg/hr, 2 mL/kg/hr, and 1 mL/kg/hr for those same weight brackets.

Does this formula apply to neonates?

The Holliday-Segar formula is most commonly used for children beyond the first 24–48 hours of life. Neonates — especially premature infants — have different fluid requirements based on gestational age, insensible losses, and organ maturity. A neonatologist should guide fluid therapy in the NICU.

Are these values appropriate for critically ill children?

Standard Holliday-Segar maintenance rates are a starting point. Critically ill patients may require restriction (e.g., cardiac failure, SIADH, ARDS) or supplementation (e.g., ongoing losses from fever, burns, diarrhea). Always individualize therapy based on clinical assessment, electrolytes, and urine output.

What fluid type should I use?

This calculator provides rate and volume only; it does not specify fluid composition. Current evidence favors isotonic fluids (0.9% NaCl or Lactated Ringer's) over hypotonic solutions for most hospitalized children to reduce the risk of hyponatremia. Consult local protocols and the patient's electrolyte status.

Can I use this for adults?

The Holliday-Segar formula is validated for pediatric patients. For adults, other maintenance fluid estimation methods (e.g., weight-based 25–30 mL/kg/day) are typically used. This tool is not designed for adult patients.

How accurate is the calculation?

The formula produces a standard estimate based on weight alone. It does not account for fever, humidity, renal function, cardiac status, or ongoing losses. Treat the result as an initial order that must be refined with clinical monitoring — urine output, serum electrolytes, and daily weights.

Pediatric Fluid Maintenance Calculator

Name: Pediatric Fluid Maintenance Calculator
Availability: InStock
Author: Nham Vu

Enter a child's weight in kg or lb to get daily (mL/day) and hourly (mL/hr) IV maintenance fluid requirements using the Holliday-Segar formula.

Patient Weight

Body Weight

Holliday-Segar Formula

First 10 kg 100 mL/kg/day

10 – 20 kg 50 mL/kg/day

Above 20 kg 20 mL/kg/day

Medical Disclaimer

This tool is for clinical education and decision support only. Results must be verified by a licensed clinician and individualized based on the patient's complete clinical picture. Do not use this calculator as the sole basis for fluid orders.

Enter patient weight and click Calculate

Daily and hourly fluid requirements will appear here

Summary

Enter a child's weight in kg or lb to get daily (mL/day) and hourly (mL/hr) IV maintenance fluid requirements using the Holliday-Segar formula.

How it works

Enter the patient's weight in kilograms or pounds; pounds are converted to kg automatically.
The calculator applies the first bracket: 100 mL/kg for each kg up to 10 kg.
The second bracket adds 50 mL/kg for each kg between 10 kg and 20 kg.
The third bracket adds 20 mL/kg for each kg above 20 kg.
The three bracket volumes are summed to give the total daily requirement (mL/day).
The daily total is divided by 24 to produce the hourly infusion rate (mL/hr).

Use cases

Determine IV maintenance fluid rate for a hospitalized child before ordering a pump setting.
Cross-check a nurse's bedside fluid calculation before infusion start.
Teach medical students and residents the Holliday-Segar three-bracket approach.
Estimate daily fluid needs for neonates and older children from a single weight entry.
Quickly recalculate when a patient's weight is updated during admission.
Screen for orders that deviate significantly from standard maintenance ranges.
Support documentation of fluid calculations in clinical notes.
Assist in PICU fluid titration discussions when baseline maintenance is needed.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu