Maintenance Fluids Calculator (Pediatric & Adult)
Calculate pediatric 4-2-1 and Holliday–Segar 100/50/20 maintenance-water estimates or adult NICE daily and hourly reference ranges.
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Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.
Input
The 500 kg (1102.312 lb) maximum is a technical data-entry guard only. It is not a guideline scope, healthy range, or validation of any clinical pathway.
About
Routine maintenance is distinct from fluid resuscitation, replacement of abnormal or ongoing losses, and redistribution. IV fluid is considered when sufficient oral or enteral intake is unavailable. This page calculates water volume only and does not generate a prescription. [2, 5]
The pediatric Holliday–Segar methods and adult NICE references come from different source frameworks and remain separate on this page. The selected pathway must come from the applicable clinical protocol. [1, 2, 5]
Formula
Interpretation
Routine maintenance only
These estimates do not include resuscitation, dehydration deficit, replacement of ongoing losses, or redistribution. [2, 5]
Pediatric methods remain separate
The 4-2-1 shortcut, its mathematical ×24 result, and the 100/50/20 daily estimate are three explicit outputs. They are not averaged, and this page does not select one automatically. [1, 6]
Adult ranges are alternatives, not a recommendation
Both ranges are displayed. This page does not determine whether frailty, renal impairment, heart failure, or refeeding risk applies, and it does not choose a range. [5]
Pediatric worked examples
| Weight | 4-2-1 | ×24 | 100/50/20 |
|---|---|---|---|
| 5 kg | 20.0 mL/hr | 480 mL/day | 500 mL/day |
| 20 kg | 60.0 mL/hr | 1440 mL/day | 1500 mL/day |
| 35 kg | 75.0 mL/hr | 1800 mL/day | 1800 mL/day |
| 40 kg | 80.0 mL/hr | 1920 mL/day | 1900 mL/day |
The three outputs remain separate. They must not be averaged and do not constitute a prescription.
Why 4-2-1 and 100/50/20 differ
Dividing the daily segment rates by 24 gives approximately 4.17, 2.08, and 0.83 mL/kg/hr. The 4-2-1 shortcut simplifies those segments to 4, 2, and 1, so its ×24 result does not always equal the daily formula. [1, 6]
Pediatric pathway and neonatal boundary
NICE provides age-banded daily volumes for term neonates from birth through day 28; this page does not implement those formulas. The AAP composition guideline covers ages 28 days through 18 years and has defined exclusions, but those limits apply to its composition recommendation rather than every Holliday–Segar volume calculation. Pediatric and adult services can overlap at ages 16–18, so the local protocol determines which framework to use. [2, 3]
Pediatric volume versus composition
NICE uses 100/50/20 for volume and recommends an initial isotonic crystalloid containing sodium 131–154 mmol/L. For its covered population, the AAP recommends isotonic maintenance fluid with appropriate potassium chloride and dextrose. In PIMS, 140 versus 77 mmol/L sodium was associated with hyponatraemia rates of 4% versus 11%. This page does not select a solution, electrolyte, or dextrose amount. [2, 3, 4]
Pediatric caps, BSA, and reduced maintenance
NICE notes that over 24 hours males rarely need more than 2500 mL and females rarely need more than 2000 mL. This page does not collect sex and does not apply either cap. NICE also describes considering a body-surface-area method for weight above the 91st centile, acute kidney injury, chronic kidney disease, or cancer, and considering 50–80% maintenance or another method when non-osmotic antidiuretic-hormone activity creates water-retention risk. This page performs none of those substitutions. [2]
Adult routine-maintenance reference
At 70 kg, 25–30 mL/kg/day gives 1750–2100 mL/day or 72.9–87.5 mL/hr; 20–25 mL/kg/day gives 1400–1750 mL/day or 58.3–72.9 mL/hr. This page does not select a range. NICE advises considering ideal body weight and lower volumes in obesity and notes that adults rarely need more than 3 L/day; the calculator does not apply an automatic cap. [5]
Adult water volume is not the complete prescription
NICE initial routine maintenance also considers approximately 1 mmol/kg/day each of sodium, potassium, and chloride, plus 50–100 g/day glucose. This page does not calculate or recommend those amounts, select fluid bags, or infer electrolyte additions from a water-volume result. An actual prescription requires monitoring and reassessment. [5]
Appropriate and unsupported uses
Appropriate arithmetic uses
- Reproduce the maintenance-water arithmetic specified by a pathway.
- Compare 4-2-1 with 100/50/20 without combining the results.
- Convert a submitted calculation weight between kg and lb.
- Teach the two adult NICE water-reference ranges.
Unsupported uses
- Resuscitation, dehydration deficit, or replacement of ongoing losses.
- Neonatal fluid calculations.
- Selecting fluid type, electrolytes, or glucose.
- Self-directed IV fluid use or generation of a final prescription.
Related calculators
- IV Drip Rate Calculator converts an already selected volume and time into a pump or gravity-drip rate; it does not determine whether the volume is appropriate.
- Pediatric Dehydration Calculator addresses a dehydration deficit, which is separate from routine maintenance.
- Ideal Body Weight Calculator provides a separate reference when an applicable adult protocol explicitly requires ideal weight; this page cannot decide whether to use it.
References
- Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823–832. PMID 13431307. doi:10.1542/peds.19.5.823.
- NICE. Intravenous fluid therapy in children and young people in hospital. NICE guideline NG29. Published 2015; updated 2020.
- Feld LG, et al. Clinical Practice Guideline: Maintenance Intravenous Fluids in Children. Pediatrics. 2018;142(6):e20183083. PMID 30478247. doi:10.1542/peds.2018-3083.
- McNab S, et al. 140 mmol/L of sodium versus 77 mmol/L of sodium in maintenance intravenous fluid therapy for children in hospital (PIMS). Lancet. 2015;385(9974):1190–1197. PMID 25472864. doi:10.1016/S0140-6736(14)61459-8.
- NICE. Intravenous fluid therapy in adults in hospital. Clinical guideline CG174. Published 2013; updated 2017.
- Meyers R. Management of Pediatric Parenteral Fluids. Journal of Pediatric Pharmacology and Therapeutics. 2024;29(4):346–353. PMID 39144385. PMCID PMC11321816. doi:10.5863/1551-6776-29.4.346.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.