Enter patient weight in kilograms
Enter weight (0.5–200 kg).
Adjust for clinical condition
Maintenance Fluid Rate
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⚠️ Medical Disclaimer: Maintenance fluid calculations are a starting point only. All IV fluid orders must be written by a licensed physician, individualized to the patient's clinical status, ongoing losses, and renal/cardiac function.
Sources & Methodology
Holliday-Segar (4-2-1) rule per original 1957 publication and AAP 2018 IV fluid guidelines.
Holliday MA & Segar WE — Pediatrics (1957)
Original publication of the 4-2-1 rule and 100/50/20 daily fluid formula. Foundation of pediatric fluid management worldwide.
AAP Clinical Practice Guideline — Maintenance IV Fluids (2018)
Recommends isotonic IV fluids (0.9% NaCl or LR) with dextrose for most hospitalized children to prevent hospital-acquired hyponatremia. aap.org
NICE Guideline NG29 — IV Fluid Therapy in Children (2020)
UK guidance on isotonic fluid selection and maintenance rate calculation. Confirms 4-2-1 rule with isotonic fluids.
4-2-1 Rule (mL/hr): 4 x first 10 kg + 2 x next 10 kg (10-20 kg) + 1 x each kg above 20 kg
100/50/20 Rule (mL/day): 100 x first 10 kg + 50 x next 10 kg + 20 x each kg above 20 kg
Divide daily by 24 to get hourly rate
100/50/20 Rule (mL/day): 100 x first 10 kg + 50 x next 10 kg + 20 x each kg above 20 kg
Divide daily by 24 to get hourly rate
25 kg patient: (4x10) + (2x10) + (1x5) = 65 mL/hr
First 10 kg: 4 x 10 = 40 mL/hr
Next 10 kg (10-20): 2 x 10 = 20 mL/hr
Remaining 5 kg (above 20): 1 x 5 = 5 mL/hr
Total: 65 mL/hr (1,560 mL/day)
Next 10 kg (10-20): 2 x 10 = 20 mL/hr
Remaining 5 kg (above 20): 1 x 5 = 5 mL/hr
Total: 65 mL/hr (1,560 mL/day)
Last reviewed: April 2026
How Are Maintenance Fluids Calculated?
The Holliday-Segar method, published in 1957, remains the standard method for calculating maintenance IV fluid requirements. The 4-2-1 rule approximates daily caloric and fluid needs based on metabolic rate, which correlates with body weight in a stepped fashion — not linearly.
The rule accounts for the fact that smaller patients have higher metabolic rates per kg and therefore higher fluid requirements per kg. A 5 kg infant needs 4 mL/kg/hr (20 mL/hr total), while a 70 kg adult only needs approximately 1.6 mL/kg/hr at the same formula.
Reference Table — Maintenance Fluid by Weight
| Weight | mL/hr (standard) | mL/day | Typical patient |
|---|---|---|---|
| 5 kg | 20 mL/hr | 480 mL | Term neonate |
| 10 kg | 40 mL/hr | 960 mL | 12-month infant |
| 20 kg | 60 mL/hr | 1,440 mL | 5-6 year child |
| 30 kg | 70 mL/hr | 1,680 mL | 10 year child |
| 50 kg | 90 mL/hr | 2,160 mL | Adolescent |
| 70 kg | 110 mL/hr | 2,640 mL | Average adult |
When to Modify Maintenance Fluids
Standard maintenance rates assume normal metabolic requirements and no extraordinary losses. Reduce to 2/3 maintenance in SIADH, post-operative fluid retention, meningitis, bronchiolitis, and cardiac failure. Increase rates in fever (add ~10% per degree above 38°C), burns, excessive sweating, and high-output states.
⚠️ Fluid Type — AAP 2018 Update: The AAP now recommends isotonic IV fluids (0.9% NaCl or Lactated Ringer's with 5% dextrose) for most hospitalized children — not hypotonic fluids (0.45% NaCl). Hypotonic fluids caused hospital-acquired hyponatremia, particularly in children with elevated ADH (post-op, CNS disease). Always add appropriate dextrose and potassium as clinically indicated.
Frequently Asked Questions
The 4-2-1 rule: 4 mL/kg/hr for first 10 kg, 2 mL/kg/hr for 10-20 kg, 1 mL/kg/hr for each kg above 20 kg. Equivalently, 100/50/20 mL/kg/day. Standard method for pediatric and adult maintenance fluid calculation since 1957.
4-2-1 rule: First 10 kg x 4, next 10 kg x 2, remainder x 1. Example 25 kg: (10x4)+(10x2)+(5x1) = 40+20+5 = 65 mL/hr = 1,560 mL/day.
Daily version of Holliday-Segar: 100 mL/kg for first 10 kg, 50 mL/kg for next 10 kg, 20 mL/kg for kg above 20. Divide by 24 for mL/hr. Gives identical results to 4-2-1 rule.
AAP 2018 recommends isotonic fluids (0.9% NaCl or LR) with 5% dextrose (D5NS or D5LR) for most hospitalized children. Avoids hospital-acquired hyponatremia caused by previously used hypotonic fluids.
Standard adult maintenance: 25-35 mL/kg/day (approx 1-1.5 mL/kg/hr). For 70 kg adult: ~70-105 mL/hr. Holliday-Segar gives 110 mL/hr for 70 kg, which is appropriate for most adults.
Reduce to 2/3 maintenance in SIADH, post-operative fluid retention, meningitis, cardiac failure, and severe renal impairment. Use isotonic fluids. Restrict further if hyponatremia is present.
SIADH causes water retention and hyponatremia. Patients need fluid restriction (2/3 or 1/2 maintenance) plus isotonic fluids. Hypotonic fluids worsen hyponatremia and can cause cerebral edema.
The standard formula applies for infants above 3-4 kg. True neonates (first week of life) need separate protocols: Day 1: 60-80 mL/kg/day, increasing daily. Preterm neonates need higher rates. Always follow neonatal protocols.
The formula plateaus at ~100 mL/hr (2,400 mL/day) for large adults, because the rate per kg above 20 kg is only 1 mL/kg/hr. Clinical needs may require adjustment beyond this.
No. Critically ill patients need individualized fluid management based on hemodynamics, organ function, and ongoing losses. Maintenance formulas are a starting point only. Physician assessment is essential.
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