Maintenance Fluids Children Calculator - Holliday-Segar 4-2-1 Rule

A maintenance fluids children calculator is a pediatric clinical tool that uses the Holliday-Segar method and the 4-2-1 rule to estimate the daily, hourly, and bolus IV fluid needs of a child by weight. It accepts pounds or kilograms so that nurses, junior doctors, and parents can all use it without converting weight by hand.

• • Pediatric IV prescribing: Confirm the maintenance mL/day and mL/hour rate to write on a fluid chart for a fasting child.
• • Two-thirds maintenance for unwell children: Pick the reduced regimen recommended for most hospitalized children who retain water under stress.
• • Resuscitation bolus planning: Pre-calculate a 20 mL/kg isotonic bolus (capped at 1 L) before approaching a child in hypovolaemic shock.
• • Teaching the Holliday-Segar method: Use the worked example to teach medical and nursing students how the 100/50/20 weight bands translate to the 4-2-1 hourly rule.

Intravenous fluid prescribing in children is more nuanced than in adults because the answer changes with every kilogram of weight. The Holliday-Segar approach, first published in 1957, remains the most widely taught starting point for stable children aged 1 month to 18 years. Our maintenance fluids children calculator implements that method in real time, with safety caps for children over 60 kg and an automatic warning for weights under 3 kg.

The calculator returns three useful numbers at once: the 24-hour fluid total, the 4-2-1 hourly infusion rate, and the 20 mL/kg bolus for shock. It also lets you choose between full, two-thirds, and half maintenance, which mirrors how pediatric teams actually prescribe fluids for children who are not eating and drinking normally.

Parents and junior clinicians who use this maintenance fluids children calculator often also reach for an Amoxicillin Pediatric Dosage Calculator to confirm a weight-based antibiotic dose for the same child.

The calculator turns the child's weight into three fluid numbers using weight-band formulas. The daily total uses the original Holliday-Segar rates of 100, 50, and 20 mL per kilogram per day. The hourly rate uses the equivalent 4, 2, and 1 mL per kilogram per hour from the 4-2-1 rule.

• Weight (kg): Body weight in kilograms after pounds-to-kg conversion. Ideal body weight is recommended for obese children.
• First 10 kg block: Contributes 100 mL/kg/day and 4 mL/kg/hour to the totals.
• Above 10 kg blocks: The second 10 kg adds 50 mL/kg/day (2 mL/kg/hour) and every kilogram above 20 kg adds 20 mL/kg/day (1 mL/kg/hour).

According to the Royal Children's Hospital Melbourne, full maintenance is 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, and 20 mL/kg/day for every kilogram above 20 kg, with a normal maximum of 2400 mL/day once a child weighs more than 60 kg.

According to the National Institute for Health and Care Excellence (NICE) guideline NG29, isotonic solutions such as sodium chloride 0.9% with 5% glucose are the preferred maintenance fluid, and the rate should be adjusted to the child's weight, clinical state, and most recent serum sodium.

According to Royal Children's Hospital Melbourne, the maintenance rate is 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, capped at 2400 mL/day

According to NICE Guideline NG29, isotonic solutions such as sodium chloride 0.9% with 5% glucose are the preferred maintenance fluid, with the rate adjusted to the child's weight, clinical condition, and recent serum sodium

The same weight-driven logic used here underlies any weight-based pediatric prescription, which is why a Pediatric Dose Calculator is a natural companion when you review a fluid and a medication order together.

These four concepts explain why the numbers are written the way they are, and they will help you communicate confidently with the rest of the clinical team when you adjust the rate.

If you compare the 4-2-1 rule to the Holliday-Segar table, the two methods are mathematically equivalent, but the hourly version is faster at the bedside because pediatric IV pumps are programmed in mL/hour, and most pediatric drug infusion charts assume the 4-2-1 hourly rate.

Because a 20 mL/kg bolus is given in response to hypotension, it helps to interpret the resulting blood pressure reading with a Pediatric Blood Pressure Calculator that classifies the value by age, sex, and height.

Five quick steps move you from a weight to a pump-ready rate and a shock bolus volume. You can rerun the calculation whenever the child's weight changes or the clinical team adjusts the maintenance fraction.

1. 1 Enter the child's weight: Type the weight you would use clinically in either pounds or kilograms. For children who are obese, use the ideal body weight recommended by the clinical team.
2. 2 Pick the maintenance regimen: Choose full, two-thirds, or half maintenance based on the child's clinical state. Two-thirds maintenance is the default for most hospitalized children.
3. 3 Read the daily total: The 24-hour total appears in mL/day and is the number to write on the fluid prescription chart or fluid balance sheet.
4. 4 Program the hourly rate: Use the mL/hour output to set the IV pump. Reassess the rate whenever the child's weight, clinical state, or serum sodium changes.
5. 5 Reserve the bolus for shock: The bolus is the volume to draw up for a child with hypovolaemic shock. Give 20 mL/kg, reassess, and repeat only if the child is still shocked.

For a 14 kg child on full maintenance, the calculator returns 1200 mL/day and 48 mL/hour. You would write 48 mL/hour on the IV fluid chart, set the pump to that volume, and only draw up the 280 mL bolus if the child became hypotensive.

The calculator saves time at the bedside, catches the dose-band transitions automatically, and shows the shock bolus alongside the maintenance rate.

• • Speed at the bedside: Replaces the mental math of multiplying by 100, 50, and 20 with a single weight entry, which is helpful on busy ward rounds.
• • Automatic unit conversion: Accepts pounds and kilograms, so parents using a bathroom scale and clinicians using a calibrated ward scale both get the same answer.
• • Built-in safety caps: Applies the 2400 mL/day and 100 mL/hour caps for children over 60 kg so that adult-sized weights never over-shoot the maintenance rate.
• • Two-thirds and half regimens: Lets the clinician switch to the reduced regimens recommended for most unwell children without re-deriving the math by hand.
• • Visible bolus calculation: Shows the 20 mL/kg resuscitation bolus on the same screen as the maintenance rate, which helps the team prepare for a sudden deterioration.

The calculator is intended as a starting point, not a replacement for clinical judgment. Serum sodium, urine output, and the child's trend should always be reviewed before the rate is left running.

If you are not sure whether a child's weight reflects healthy growth, a Child Weight Percentile Calculator places the number on the appropriate growth curve before you trust the maintenance rate it produces.

Several patient and clinical factors change the maintenance rate you should actually prescribe, even though the Holliday-Segar table gives a single starting number. Adjust the regimen or revisit the weight used in the calculation when any of the following apply.

• • The calculator assumes a stable child between 1 month and 18 years who cannot yet take enteral fluids. It is not designed for neonates, children in shock, or children with cardiac, renal, hepatic, or oncologic conditions.
• • Maintenance fluids do not include replacement of ongoing losses such as gastric drain output or diarrhoea. Those volumes must be measured and replaced separately using isotonic fluid.

According to Royal Children's Hospital Melbourne, the majority of unwell children retain water and should be prescribed two-thirds of the calculated maintenance rate unless clearly dehydrated, with isotonic sodium chloride 0.9% with 5% glucose as the preferred maintenance fluid

For clinically obese children the Holliday-Segar rate should be based on adjusted body weight rather than actual weight, and a Adjusted Weight Calculator shows the corrected value to enter into the maintenance fluids children calculator.