Nursing care
Holliday-Segar method: calculating pediatric maintenance fluids with the 4-2-1 rule
Written and reviewed by Hannah Nguyen, MSN, RN, CPN · 4 min read · Updated November 2026
Short answer
The Holliday-Segar method estimates a child's maintenance fluid from body weight: 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. The hourly version, called the 4-2-1 rule, uses 4, 2 and 1 mL/kg/hr for the same three weight bands.
The formula, daily and hourly
Holliday and Segar published the method in Pediatrics in 1957 as an estimate of the daily water a child needs when receiving fluids by vein. The MSD Manual still uses it and gives both the daily and the hourly form shown below.
| Weight | Per day | Per hour (4-2-1) |
|---|---|---|
| 0 to 10 kg | 100 mL/kg | 4 mL/kg |
| 11 to 20 kg | 1,000 mL plus 50 mL for each kg over 10 | 40 mL plus 2 mL for each kg over 10 |
| Over 20 kg | 1,500 mL plus 20 mL for each kg over 20 | 60 mL plus 1 mL for each kg over 20 |
The bands are cumulative. A 25 kg child does not get 20 mL/kg for all 25 kg; the first 10 kg are counted at the top rate, the next 10 at the middle rate, and only the last 5 at the lowest. Applying one rate to the whole weight is the classic wrong answer.
Worked examples
All weights below are practice figures, not orders. Work in kilograms, convert pounds by dividing by 2.2, and carry mL/kg units through every line so the leftover unit is mL per day or mL per hour.
Worked example
- All 8 kg fall in the first band
- 4 mL/kg/hr x 8 kg = 32 mL/hr
- Daily check: 100 mL/kg/day x 8 kg = 800 mL/day
Worked example
- Daily: first 10 kg = 1,000 mL; next 10 kg = 500 mL; last 5 kg x 20 = 100 mL
- Daily total = 1,600 mL/day; divided by 24 = 66.7 mL/hr
- Hourly: 40 + 20 + 5 = 65 mL/hr
Worked example
- 44 lb / 2.2 = 20 kg
- First 10 kg x 4 = 40 mL/hr
- Next 10 kg x 2 = 20 mL/hr
Why the daily and hourly answers differ slightly
The 4-2-1 rule is a rounded shortcut. Multiplying 4, 2 and 1 mL/kg/hr by 24 gives 96, 48 and 24 mL/kg/day, close to but not exactly 100, 50 and 20. That is why the 25 kg child comes out at 65 mL/hr one way and 66.7 mL/hr the other.
Neither answer is wrong in practice, but on an exam use the method the question names. If the stem asks for mL per day, use 100-50-20; if it asks for an hourly pump rate and names the 4-2-1 rule, use that and do not convert from the daily total.
What the number does not tell you
Holliday-Segar gives a volume, not a fluid type. The American Academy of Pediatrics 2018 guideline recommends isotonic solutions with appropriate potassium chloride and dextrose for maintenance fluids in patients from 28 days to 18 years, because they lower the risk of hyponatremia; neonates and some groups with specific conditions are excluded.
The MSD Manual notes that hospitalized children given traditional hypotonic fluids have developed hyponatremia linked to ADH release, so serum electrolytes need close monitoring. For the nurse, that means trending daily weight, intake and output, and sodium results, and reporting new irritability, vomiting or lethargy. Maintenance also covers only ongoing daily need; a dehydrated child needs the deficit replaced as well, per the prescriber's plan.
Sources and further reading
MSD Manual Professional Version: Dehydration in Children. Holliday-Segar daily and hourly maintenance rates by weight band, AAP isotonic recommendation, hyponatremia with hypotonic fluids from ADH release, electrolyte monitoring.
Europe PMC records: Feld et al. 2018 AAP Clinical Practice Guideline on Maintenance IV Fluids; Holliday and Segar 1957. AAP guideline age range 28 days to 18 years, isotonic fluids with potassium chloride and dextrose to reduce hyponatremia, exclusion of neonates and specific conditions; original 1957 Pediatrics paper by Holliday and Segar.
Open RN Nursing Skills: Weight-Based Calculations. Pound to kilogram conversion (1 kg = 2.2 lb) and carrying units through weight-based calculations.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pediatrics practice questions are the closest set to what this page covers.
Common questions
What is the 4-2-1 rule for fluids?
It is the hourly form of the Holliday-Segar method: 4 mL/kg/hr for the first 10 kg of body weight, 2 mL/kg/hr for the next 10 kg, and 1 mL/kg/hr for each kg above 20. A 30 kg child, for example, works out to 40 + 20 + 10 = 70 mL/hr.
How do you calculate pediatric maintenance fluids?
Convert weight to kilograms, then apply 100 mL/kg/day to the first 10 kg, 50 mL/kg/day to the next 10 kg and 20 mL/kg/day to each kg above 20. Add the bands together. Divide by 24 for an hourly rate, or use the 4-2-1 rule directly.
Does the Holliday-Segar method apply to newborns?
The AAP maintenance fluid guideline covers patients from 28 days to 18 years and excludes younger neonates, whose fluid needs change day by day after birth. Neonatal units follow their own protocols, so do not assume the 4-2-1 rule applies to a newborn question.