π§ Pediatric Maintenance Fluids Calculator
Holliday-Segar daily totals and the 4-2-1 hourly rule.
For informational purposes only, not medical advice. Consult a healthcare professional.
The Holliday-Segar method estimates a child's daily maintenance fluid needs from weight: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg beyond 20 kg. The 4-2-1 rule is the same math expressed hourly: 4 mL/kg/hr for the first 10 kg, 2 for the next 10, 1 beyond. Both come from Holliday and Segar's 1957 Pediatrics paper linking fluid needs to caloric expenditure.
Enter weight in kilograms. The calculator returns the 24-hour total and the hourly pump rate, capped at typical maximums. This covers maintenance only: deficits, ongoing losses, and special conditions are added separately by the clinical team.
How to Use This Calculator
Weigh the child in kilograms. Enter the weight. Read the daily total and hourly rate. Set the pump to the hourly rate and confirm the fluid type with the team: current guidelines favor isotonic fluids (like normal saline or balanced crystalloids) over hypotonic ones for most hospitalized children.
Enter the child's weight in kg.
Read the 24-hour Holliday-Segar total.
Read the hourly 4-2-1 pump rate.
Confirm fluid type and any added electrolytes with the clinical team.
The 100-50-20 and 4-2-1 Rules
Hourly: 4 mL/kg/hr + 2 + 1 for the same bands
Holliday and Segar observed that water needs track energy expenditure: roughly 100 mL per 100 kcal burned. A 10 kg infant burns about 100 kcal/kg/day, hence 100 mL/kg; larger children burn fewer calories per kilo, hence the tapering 50 and 20 bands. The 4-2-1 rule is just the daily formula divided by 24, rounded to memorable integers. The 2,400 mL/day cap reflects that maintenance needs plateau near adult values. Modern practice has shifted the default fluid from hypotonic to isotonic after trials showed hypotonic maintenance caused hospital-acquired hyponatremia.
Worked Example
An 18 kg child: the first 10 kg give 1,000 mL and the next 8 kg give 400 mL, totaling 1400 mL/day, or 56 mL/hr (4-2-1 rule). The hourly 4-2-1 math agrees: 40 mL for the first 10 kg plus 16 mL for the next 8 kg equals 56 mL/hr. A 30 kg child would get 1,700 mL/day at 70 mL/hr.
What the Numbers Cover (and Do Not)
Maintenance replaces normal daily losses: urine, stool, skin, and lungs. It does not replace dehydration deficits (calculated separately by percent dehydration), ongoing abnormal losses (vomit, diarrhea, drains, burns), or third-spacing. Fever, tachypnea, and radiant warmers raise needs; kidney failure, heart failure, and SIADH lower them. The calculator's number is the starting point the team adjusts, not the final order.
Orders Belong to the Clinical Team
Pediatric fluid orders require a prescriber: this calculator checks the arithmetic behind them. Dehydrated, critically ill, or post-surgical children need individualized plans. Never set an infusion pump from a web calculator without a matching medical order. For informational purposes only, not medical advice. Consult a healthcare professional.
Related tools: IV flow rate calculator and mean arterial pressure.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the 4-2-1 rule?
The hourly version of Holliday-Segar: 4 mL/kg/hr for the first 10 kg, 2 for the next 10 kg, 1 for each kg beyond 20.
What is the Holliday-Segar formula?
Daily maintenance fluids: 100 mL/kg for the first 10 kg, 50 for the next 10, 20 beyond 20 kg. Published in Pediatrics in 1957.
What fluids are used for pediatric maintenance?
Current guidelines favor isotonic fluids (normal saline or balanced crystalloids) over hypotonic fluids, which caused hyponatremia in hospitalized children.
Is there a maximum maintenance rate?
Commonly capped around 100 mL/hr or 2,400 mL/day, near adult maintenance values. The team individualizes beyond that.
Do these rules apply to neonates?
With caution. Neonates, especially preterm infants, have very different fluid and electrolyte needs and are managed with dedicated protocols.
What about fluid boluses?
Boluses for dehydration or shock are separate: typically 20 mL/kg isotonic, reassessed after each, on top of maintenance.
Why did guidelines move away from hypotonic fluids?
Trials showed hypotonic maintenance caused hospital-acquired hyponatremia, sometimes with seizures. Isotonic fluids proved safer for most children.
Does fever increase fluid needs?
Yes. Insensible losses rise with fever and tachypnea, so maintenance is often increased 10-12% per degree above normal, per team judgment.
Do maintenance fluids include what the child drinks?
The Holliday-Segar number is the total water need, so oral intake counts toward it. A child drinking well needs less IV fluid; the IV rate is the gap between the calculated need and what they take by mouth. Reassess often, because a child who starts drinking again may need the IV turned down or off.
Why do guidelines now prefer isotonic fluids for children?
The original 1957 guidance used hypotonic fluids, but hospitalized children make extra antidiuretic hormone from pain, nausea, and stress, which makes them retain free water. Hypotonic fluids plus that hormone state caused dangerous low sodium in some children. Isotonic fluids (like normal saline or Lactated Ringer's) avoid adding free water, so they are now the standard.