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Maintenance IV fluids calculator (4-2-1 rule)
For clinicians and students. Not a substitute for your institution’s protocols.
Maintenance fluids by the Holliday-Segar method are 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 kg above 20. As an hourly rate, that’s the 4-2-1 rule: 4, 2 and 1 mL/kg/h. The AAP recommends isotonic fluids for most children aged 28 days to 18 years.
Source: Pediatrics 1957;19(5):823-832 · American Academy of Pediatrics
Calculate maintenance fluids
What maintenance doesn’t include
- Deficit replacement for dehydration, ongoing losses (vomiting, diarrhea, drains), and fluids given with medications.
- Conditions where maintenance should be restricted or specialist-guided, such as those excluded by the AAP guideline: neurosurgical disorders, heart, liver or kidney disease, cancer, diabetes insipidus, severe burns, voluminous watery diarrhea, and neonates under 28 days.
Common questions
What is the 4-2-1 rule?
An hourly maintenance fluid rate: 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the next 10 kg, and 1 mL/kg/h for each kg above 20. A 25 kg child gets 40 + 20 + 5 = 65 mL/h.
What is the Holliday-Segar method?
The daily version of the same rule: 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, and 20 mL/kg/day above 20 kg. Holliday and Segar published it in 1957.
Which fluid should be used for maintenance?
The AAP’s 2018 guideline recommends isotonic solutions with appropriate potassium chloride and dextrose for most patients aged 28 days to 18 years, because hypotonic fluids increase the risk of hyponatremia. It lists exclusions, including neonates under 28 days.
Sources
- The maintenance need for water in parenteral fluid therapy (Holliday, Segar). Pediatrics 1957;19(5):823-832. Checked 2026-09-25.
- Clinical Practice Guideline: Maintenance Intravenous Fluids in Children (Feld et al.). American Academy of Pediatrics, Pediatrics 2018;142(6):e20183083. Checked 2026-09-25.