What is the Holliday-Segar method?

The Holliday-Segar method is the most widely used formula for estimating daily fluid maintenance requirements in children. It assigns 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 additional kilogram above 20 kg.

What is the 4-2-1 rule?

The 4-2-1 rule is a bedside hourly shortcut based on the Holliday-Segar formula: 4 mL/kg/hour for the first 10 kg, 2 mL/kg/hour for the next 10 kg, and 1 mL/kg/hour for each kg above 20 kg. Because 4 mL/kg/hour equates to 96 mL/kg/day rather than exactly 100 mL/kg/day, calculating total daily Holliday-Segar volume divided by 24 yields a slightly different hourly rate (e.g., 41.7 mL/hour vs 40 mL/hour for 10 kg).

Is this calculator suitable for adults?

The Holliday-Segar formula was developed for pediatric patients. For adults, most clinicians use a fixed rate (e.g., 25–30 mL/kg/day) or disease-specific protocols. This calculator can still compute values for adult weights, but clinical judgment is always required.

Does this account for ongoing losses or dehydration?

No. This calculator provides maintenance fluids only — the baseline volume needed to replace insensible and obligate losses in a normally hydrated patient. Deficit replacement, ongoing losses (e.g., diarrhea, drainage), and disease-specific adjustments must be calculated and added separately.

What fluid type should be used for maintenance?

Fluid type selection (e.g., 0.9% NaCl, 0.45% NaCl + dextrose, lactated Ringer's) depends on the clinical scenario, electrolytes, and institutional protocol. This calculator outputs rate only, not fluid composition.

Is the result the same whether I use kg or lbs?

Yes. When you select pounds, the calculator converts to kilograms first (1 lb = 0.453592 kg) before applying the formula, so the result is equivalent.

Fluid Maintenance Calculator

Enter a patient's weight to instantly calculate daily IV fluid maintenance requirements using the Holliday-Segar (4-2-1) method.

Patient Weight

Unit

Weight (kg)

Quick presets (kg)

Enter a weight above and click Calculate to see the fluid maintenance rate.

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Summary

The Fluid Maintenance Calculator uses the Holliday-Segar method — also known as the 4-2-1 rule — to determine the daily and hourly IV fluid maintenance rate for pediatric patients based on body weight. It applies 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg for every kilogram above 20 kg. Results are displayed in both mL/day and mL/hour for quick clinical reference.

How it works

Enter the patient's weight in kilograms or pounds.
The calculator applies the Holliday-Segar 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.
Total daily volume (mL/day) is computed by summing each weight segment.
The hourly rate (mL/hour) is derived by dividing the daily volume by 24.
Results are shown instantly with a step-by-step breakdown of the calculation.

Use cases

Calculate maintenance IV fluids for hospitalized pediatric patients.
Verify fluid orders during ward rounds or handover.
Quick reference for medical students and nursing staff.
Check dosing accuracy before administering maintenance fluids.
Educational tool for learning the 4-2-1 rule.
Use during PALS or ATLS simulation training.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu