IV Fluid Drip Rate & Maintenance Fluid Calculator (4-2-1 Holliday-Segar Rule)
Calculate maintenance IV fluid requirements (mL/hr) using the 4-2-1 rule and IV drip rates (drops/min) based on tubing drop factor.
IV Fluid Calculator
Enter values below to calculate
This calculator is for informational and educational purposes. Results should be interpreted with clinical judgment and local guidelines.
What is the 4-2-1 Rule for Maintenance IV Fluids?
The 4-2-1 Rule (Holliday-Segar Method) is the clinical gold standard formula developed by Malcolm Holliday and William Segar in 1957 to calculate hourly maintenance intravenous (IV) fluid requirements based on body weight. Maintenance fluids replace normal daily physiologic water losses (insensible cutaneous/respiratory losses, urine, stool). The rule allocates: 4 mL/kg/hr for the first 10 kg of body weight, 2 mL/kg/hr for the next 10 kg (11–20 kg), and 1 mL/kg/hr for every kg above 20 kg. For total daily volume (24 hours), the equivalent 100-50-20 rule allocates 100 mL/kg/day for first 10 kg, 50 mL/kg/day for 11–20 kg, and 20 mL/kg/day for > 20 kg.
4-2-1 Rule (Hourly): First 10 kg = 4 mL/kg/hr; Next 10 kg (11–20) = +2 mL/kg/hr; Each kg > 20 kg = +1 mL/kg/hr. Drip Rate (gtt/min) = [Total Volume (mL) × Drop Factor (gtt/mL)] / [Time (minutes)].
When to Use the IV Fluid Calculator
- Calculating maintenance IV fluid rate (mL/hr) for pediatric and adult surgical or medical inpatients NPO (nothing by mouth).
- Converting prescribed hourly infusion rates (mL/hr) into manual IV drip rates (drops/min or gtt/min) when infusion pumps are unavailable.
- Adjusting fluid rates for fever (+10–12% per °C above 37°C) or renal/heart failure restrictions.
Holliday-Segar 4-2-1 Formula & Drip Rate Equations
Hourly Maintenance Fluid Rate (4-2-1 Rule)
Rate (mL/hr) = (10kg × 4) + ((Next 10kg) × 2) + ((Weight − 20kg) × 1)
Patient weight = 60 kg: (10×4) + (10×2) + (40×1) = 40 + 20 + 40 = 100 mL/hr
IV Drip Rate Formula (Drops per minute)
Drip Rate (gtt/min) = [Infusion Rate (mL/hr) × Drop Factor (gtt/mL)] / 60 minutes
Rate = 100 mL/hr, Macrodrip tubing (15 gtt/mL): (100 × 15) / 60 = 25 drops/min
Variables
Patient Weight (kg)
Body weight in kilograms.
Tubing Drop Factor (gtt/mL)
Macrodrip: 10, 15, or 20 gtt/mL. Microdrip (Pediatric): 60 gtt/mL.
Microdrip tubing (60 gtt/mL) has a 1:1 mathematical relationship where drip rate in gtt/min equals mL/hr infusion rate.
Tubing Drop Factor Reference Table
Standard IV administration set specifications.
| Range | Classification | Health Risk |
|---|---|---|
| Microdrip (Pediatric) | 60 gtt/mL | gtt/min equals mL/hr exactly. Used in pediatric & ICU micro-infusions. |
| Macrodrip (Standard 15) | 15 gtt/mL | Standard adult gravity tubing set. |
| Macrodrip (Standard 20) | 20 gtt/mL | Common adult gravity infusion tubing set. |
| Blood Set / Heavy Drop | 10 gtt/mL | Used for blood product transfusion and viscous fluids. |
In fluid overload states (CHF, ESRD, severe hyponatremia), maintenance rates must be restricted to 50–75% of calculated values.
Limitations & Clinical Warnings
The 4-2-1 rule provides baseline MAINTENANCE fluids, NOT fluid resuscitation for hypovolemic shock (use 20 mL/kg bolus in pediatrics, 30 mL/kg in sepsis).
Hypotonic fluids (0.45% Saline) can cause severe iatrogenic hyponatremia in hospitalized children due to elevated non-osmotic ADH secretion; isotonic fluids (0.9% Normal Saline or Plasmalyte) are preferred per AAP guidelines.
Medical Disclaimer
Always monitor serum sodium, electrolyte balance, and urine output during continuous IV fluid administration.
References & Citations
- Holliday MA, Segar WE. “The maintenance need for water in parenteral fluid therapy”. Pediatrics. 1957. 19(5): 823–832. PMID: 13431307
- Feld LG, Neuspiel DR, Foster BA, et al.. “Clinical Practice Guideline: Maintenance Intravenous Fluids in Children (AAP Guidelines)”. Pediatrics. 2018. 142(6): e20183083. PMID: 30478056 | DOI: 10.1542/peds.2018-3083
Medically Reviewed
Reviewed by CliniqWise Clinical Advisory Board — Nursing & Critical Care Panel · Last updated: 2026-08-27 · Next review: 2027-02-27
Common Questions About IV Fluid Calculator
Explore More Medical Calculators
Browse the CliniqWise calculator library by specialty, score, disease area, or clinical task.
Browse All Calculators