Heart Score Calculator
Pediatric formula · Reviewed August 2026

Maintenance Fluid Calculator

Enter a child's weight to calculate maintenance fluid by the 4-2-1 hourly rule and the Holliday-Segar 100-50-20 daily method. Both estimates and each weight band are shown separately.

Quick formulas: 4, 2, then 1 mL/kg/hour across the first 10 kg, next 10 kg, and weight above 20 kg. Daily method: 100, 50, then 20 mL/kg/day across those bands.
4-2-1
Hourly Rule
100-50-20
Daily Method
kg
Weight Input

For educational calculation support in children 28 days to 18 years—not for newborns, adults, shock, dehydration replacement, burns, boluses, ongoing losses, or a complete IV fluid order. A clinician must assess whether maintenance fluid is indicated and select its composition and monitoring.

Pediatric weight-based estimate

Enter Body Weight

Calculated locally
Weight units
Patient weight

The calculator does not ask for age because both formulas use weight alone. Confirm separately that the patient and clinical situation fit the method.

Try an example:

What Is a Maintenance Fluid Calculation?

A maintenance fluid calculation estimates the water needed to cover ordinary physiologic losses when a child cannot take enough fluid by mouth or enteral feeding. Maintenance IV fluid is often shortened to MIVF. It is a baseline estimate, not a measure of dehydration and not the total volume needed in every illness.

The classic Holliday-Segar method links water needs to estimated energy expenditure and expresses the result using three weight bands. It remains a familiar way to calculate pediatric maintenance fluids because it needs only body weight and produces an auditable result.

If the question is an already-existing water deficit caused by hypernatremia, use the Free Water Deficit Calculator. Deficit replacement and routine maintenance are different calculations and should not be added blindly.

Maintenance Fluid Formulas

Daily Holliday-Segar100-50-20

First 10 kg: 100 mL/kg/day
Next 10 kg: 50 mL/kg/day
Above 20 kg: 20 mL/kg/day

Hourly shorthand4-2-1

First 10 kg: 4 mL/kg/hr
Next 10 kg: 2 mL/kg/hr
Above 20 kg: 1 mL/kg/hr

Important: the rules are related, but they are not exact conversions. Multiplying 4-2-1 by 24 gives 96-48-24 mL/kg/day—not 100-50-20. This calculator preserves that distinction instead of forcing one result to match the other.

How to Calculate Maintenance Fluids

  1. 1

    Confirm the calculation is maintenance-only

    Do not use this formula for shock, a resuscitation bolus, dehydration deficit, burn resuscitation, or replacement of abnormal ongoing losses.

  2. 2

    Convert weight to kilograms

    If weight is in pounds, divide by 2.20462. The calculator converts units before applying either method.

  3. 3

    Split weight into three bands

    Allocate up to 10 kg to the first band, up to another 10 kg to the second, and any remaining weight to the third.

  4. 4

    Apply the daily factors

    Multiply the three bands by 100, 50, and 20 mL/kg/day, then add them for the Holliday-Segar daily estimate.

  5. 5

    Apply the hourly factors

    Multiply the same bands by 4, 2, and 1 mL/kg/hour, then add them for the 4-2-1 hourly estimate.

  6. 6

    Reassess clinical context

    Illness, organ function, fluid intake, urine output, medications, and abnormal losses may make a standard maintenance estimate inappropriate.

Maintenance Fluid Calculation Example

Example: child weighing 25 kg
  1. 1

    Daily first band: 10 × 100 = 1,000 mL/day

  2. 2

    Daily second band: 10 × 50 = 500 mL/day

  3. 3

    Daily third band: 5 × 20 = 100 mL/day

  4. 4

    Holliday-Segar total: 1,600 mL/day, averaging 66.7 mL/hr

  5. 5

    4-2-1 hourly total: (10 × 4) + (10 × 2) + (5 × 1) = 65 mL/hr

The hourly rule has a daily equivalent of 1,560 mL for this example. That is 40 mL/day, or 2.5%, lower than the 1,600 mL Holliday-Segar daily estimate. The difference is expected because the hourly factors are rounded shorthand.

4-2-1 Rule by Weight

1–10 kg4 × weight

mL/hour

8 kg = 32 mL/hr
10.1–20 kg40 + 2 × (kg − 10)

mL/hour

15 kg = 50 mL/hr
Above 20 kg60 + 1 × (kg − 20)

mL/hour

25 kg = 65 mL/hr

The factors are cumulative. A 15 kg child does not receive 2 mL/kg/hour for all 15 kg; the first 10 kg remain in the 4 mL/kg/hour band, and only the next 5 kg use 2 mL/kg/hour.

How to Interpret the Results

Calculator includes

Baseline water estimate

Weight conversion, three formula bands, a daily result, an hourly result, and the mathematical difference between methods.

Calculator excludes

Individual fluid prescription

Clinical indication, solution composition, route, deficit, boluses, ongoing losses, fluid restriction, and laboratory monitoring.

A calculated rate is not automatically the rate that should be administered. Hospitalized children may produce more antidiuretic hormone during pain, nausea, surgery, pulmonary disease, or central nervous system illness, reducing their ability to excrete free water. Conversely, fever, tachypnea, high urine output, or gastrointestinal loss may increase needs.

Serum sodium and glucose influence fluid safety but are not inputs to this maintenance-volume formula. The Serum Osmolality Calculator answers a separate concentration question; it does not choose a maintenance rate.

Pediatric Maintenance IV Fluid Guidance

The American Academy of Pediatrics guideline on maintenance intravenous fluids addresses children 28 days through 18 years who need maintenance IV fluid in acute-care settings. For most included patients, it recommends isotonic solutions with appropriate potassium chloride and dextrose to reduce hospital-acquired hyponatremia.

That recommendation concerns fluid composition and applies to defined populations; the arithmetic on this page concerns volume. This calculator intentionally does not generate an order or tell a user which solution, potassium amount, dextrose concentration, or infusion duration to use.

Population limits: the AAP guideline excludes neonates younger than 28 days or in the NICU and children with several higher-risk conditions, including renal dysfunction, cardiac or hepatic disease, cancer, diabetes insipidus, voluminous watery diarrhea, severe burns, and neurosurgical disorders. A separate GFR Calculator cannot make a standard maintenance formula appropriate when renal function is impaired.

What Is Not Included in Maintenance Fluid

  • Resuscitation: shock and poor perfusion require urgent assessment; maintenance fluid is not a bolus formula.
  • Dehydration deficit: a pre-existing deficit needs a separate assessment and replacement plan.
  • Ongoing losses: urine, diarrhea, vomiting, drains, and bleeding are not predicted by body weight alone.
  • Nutrition: calculated maintenance water does not establish adequate calories, protein, or micronutrients.
  • Fluid composition: sodium, chloride, potassium, glucose, and tonicity require separate clinical decisions.
  • Monitoring: intake, output, weight, examination, electrolytes, and glucose may require repeated review.

Maintenance Fluid Calculation for Adults

Adult fluid assessment is a different search intent from the pediatric 4-2-1 and Holliday-Segar calculation. Adult practice commonly starts with a daily mL/kg estimate and then adjusts for age, frailty, heart failure, kidney impairment, liver disease, obesity, oral intake, and ongoing losses. This pediatric calculator does not offer an adult mode because presenting the same output as a universal adult prescription would hide those differences.

Common Maintenance Fluid Calculation Errors

  • Using pounds as kilograms: this overstates the calculated volume by more than twofold.
  • Applying one factor to all weight: the rules use cumulative bands, not a single rate chosen from a table.
  • Assuming both methods are identical: 4-2-1 multiplied by 24 is not exactly 100-50-20.
  • Adding a deficit without assessment: maintenance, deficit, bolus, and ongoing-loss replacement are separate components.
  • Using the formula for a neonate: newborn fluid needs change with postnatal age and require neonatal guidance.
  • Ignoring changes over time: a child's weight, intake, urine output, losses, and laboratory results can change after the first calculation.

When an Online Calculator Is Not Enough

Fluid decisions can become urgent when a child has altered mental status, breathing difficulty, poor perfusion, very low urine output, persistent vomiting or diarrhea, severe burns, significant bleeding, or cannot keep fluids down. These situations need clinical assessment rather than a routine maintenance estimate.

Call 911 in the United States for severe breathing difficulty, collapse, unresponsiveness, a seizure, blue or gray color, or other signs of a medical emergency. For non-emergency concerns, contact the child's clinician or local urgent-care service.

Maintenance Fluid Calculator FAQs

How do you calculate pediatric maintenance fluids?

Use weight in kilograms. The daily Holliday-Segar method assigns 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. The hourly 4-2-1 rule assigns 4, 2, and 1 mL/kg/hour across the same bands.

What is the difference between the 4-2-1 rule and the 100-50-20 method?

They use the same weight bands but different rounded rates. Multiplying 4-2-1 by 24 gives 96-48-24 mL/kg/day, so its daily equivalent is not always identical to the 100-50-20 daily estimate. This calculator reports both separately.

Can this maintenance fluid calculator be used for adults?

This calculator is pediatric-focused. Although the arithmetic can return a number for any entered weight, adult maintenance fluid prescribing commonly uses different assessment methods and must consider comorbidities, organ function, intake, and losses.

Does the result include dehydration, boluses, or ongoing losses?

No. It estimates baseline maintenance only. It does not calculate resuscitation boluses, an existing dehydration deficit, replacement of ongoing urine or gastrointestinal losses, or a total fluid prescription.

Can the calculator be used for newborns or neonates?

No. Neonates younger than 28 days and infants in neonatal intensive care require age-specific fluid management. The AAP maintenance intravenous fluid guideline discussed on this page starts at 28 days of age and excludes neonates.

Evidence and Editorial Notes

The formulas, pediatric scope, separation of maintenance from other fluid components, and limitations were checked against original literature and current pediatric guidance.

  1. Holliday MA, Segar WE. The Maintenance Need for Water in Parenteral Fluid Therapy. Pediatrics. 1957.
  2. Feld LG, et al. Clinical Practice Guideline: Maintenance Intravenous Fluids in Children. Pediatrics. 2018.
  3. Holliday-Segar original record. PubMed PMID 13431307. U.S. National Library of Medicine.

Last formula and source review: August 12, 2026. Calculations run in your browser. Values entered in this form are not sent to our server.

Formula and source review

Dr. Heart (Health Observer)

Dr. Heart reviews the formulas, sources, intended uses, and limits presented across Heart Score Calculator. Each tool is checked against published references and explained in clear language. Dr. Heart is an editorial persona, not a licensed physician or a substitute for individualized medical care.

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