Maintenance IV Fluids Calculator (4-2-1 Rule)
Calculate maintenance fluid rates using the Holliday-Segar 4-2-1 rule: 4 mL/kg/hr for first 10kg, 2 mL/kg/hr for next 10kg, 1 mL/kg/hr for each kg above 20kg. Applies to both pediatric and adult patients.
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Applies to pediatric and adult patients.
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Why: Applies to pediatric and adult patients.
How: Enter your values in the calculator fields below, keep units consistent, then run the calculation to see results and any step-by-step work shown on this page.
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For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
Calculate maintenance fluid rates using the Holliday-Segar 4-2-1 rule: 4 mL/kg/hr for first 10 kg, 2 mL/kg/hr for next 10 kg, 1 mL/kg/hr for each kg above 20 kg. Applies to both pediatric and adult patients. Based on caloric expenditure (100 kcal/kg first 10 kg, 50 for next 10, 20 thereafter).
Sources: Holliday-Segar 1957, AAP, UpToDate Pediatrics.
Key Takeaways
- • 4-2-1 rule: 4 + 2 + 1 mL/kg/hr for each weight tier
- • Daily: 100 + 50 + 20 mL/kg/day for same tiers
- • Restrict in cardiac, renal, SIADH
- • Replace ongoing losses (vomiting, diarrhea) mL for mL
Did You Know?
How Does the 4-2-1 Rule Work?
Hourly Rate (4-2-1)
First 10 kg × 4 + next 10 kg × 2 + remaining kg × 1. Example: 25 kg = 40 + 20 + 5 = 65 mL/hr.
Daily Rate (100-50-20)
First 10 kg × 100 + 10-20 kg × 50 + >20 kg × 20 mL/kg/day. Same metabolic basis.
Adjustments
Add fever (~10%), replace losses, apply restriction (50-75%) for cardiac/renal.
Expert Tips
4-2-1 Rule Quick Reference
| Weight (kg) | mL/hr | mL/day |
|---|---|---|
| 5 | 20 | 500 |
| 10 | 40 | 1000 |
| 15 | 50 | 1250 |
| 20 | 60 | 1500 |
| 25 | 65 | 1600 |
| 30 | 70 | 1700 |
| 50 | 90 | 2100 |
| 70 | 110 | 2600 |
Frequently Asked Questions
What is the 4-2-1 rule?
The Holliday-Segar 4-2-1 rule calculates hourly maintenance IV fluid rate: 4 mL/kg/hr for first 10 kg, 2 mL/kg/hr for next 10 kg, 1 mL/kg/hr for each kg above 20 kg. Example: 25 kg = 40 + 20 + 5 = 65 mL/hr.
How is maintenance fluid calculated?
Daily: First 10 kg × 100 mL/kg/day + 10-20 kg × 50 mL/kg/day + >20 kg × 20 mL/kg/day. Hourly (4-2-1): First 10 kg × 4 + next 10 kg × 2 + remaining × 1 mL/kg/hr.
When should maintenance fluids be restricted?
Restrict to 50-75% in: cardiac impairment, renal failure, SIADH, post-op with fluid overload, and certain neurosurgical cases. Monitor for hyponatremia with hypotonic fluids.
What fluid type for maintenance?
Pediatrics: D5 0.45NS or D5 0.9NS with KCl 20 mEq/L. Neonates: D10W. Avoid hypotonic fluids (D5W, 0.2NS) as sole maintenance—hyponatremia risk.
How do I replace ongoing losses?
Replace vomiting with 0.45NS + KCl. Replace diarrhea with solution containing bicarbonate. Replace drain output mL for mL. Add fever adjustment (~10% per degree above 37°C).
What are electrolyte requirements?
Standard: Na+ 3 mEq/100 mL, K+ 2 mEq/100 mL. Adjust for hypokalemia (add KCl), hyponatremia (use NS), or renal impairment (hold K+ until output adequate).
Key Statistics
Official Data Sources
⚠️ Disclaimer: This calculator is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider. Fluid management requires clinical judgment based on individual patient factors.
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