Last verified · v1.0

Calculator · health

Pediatric Maintenance Fluids Calculator (Holliday Segar)

Pediatric maintenance fluids calculator using the Holliday-Segar method. Enter body weight to get the 4-2-1 hourly rate or 100-50-20 daily volume instantly.

FreeInstantNo signupOpen source

Inputs

Child's Weight

Output Rate

Maintenance Fluid Rate

—

Get a plain-English breakdown of your result with practical next steps.

Maintenance Fluid Rate—mL

The formula

How the
result is
computed.

What Is the Holliday-Segar Method?

The Holliday-Segar method is the clinical gold standard for estimating maintenance fluid requirements in pediatric patients. Introduced in 1957 by physicians Malcolm Holliday and William Segar, the formula correlates a child's caloric expenditure with water needs — establishing that approximately 100 mL of water is required for every 100 kcal metabolized per day. This physiologic relationship produces a tiered, weight-based formula that remains the foundational tool in pediatric fluid management worldwide.

The Two Equivalent Expressions of the Formula

Clinicians apply the Holliday-Segar formula in two interchangeable forms, chosen based on the clinical setting:

4-2-1 Rule (Hourly Infusion Rate)

4 mL/kg/hr — for the first 10 kg of body weight
2 mL/kg/hr — for the next 10 kg (body weight 10.1 to 20 kg)
1 mL/kg/hr — for every kilogram above 20 kg

100-50-20 Rule (Total Daily Volume)

100 mL/kg/day — for the first 10 kg
50 mL/kg/day — for the next 10 kg (10.1 to 20 kg)
20 mL/kg/day — for each kilogram above 20 kg

The 4-2-1 rule is the preferred expression in inpatient settings where continuous IV infusion rates are prescribed. The 100-50-20 rule suits total daily fluid planning and oral rehydration contexts. While the two rules are clinically equivalent, their mathematical relationship is approximate rather than exact — 4 × 24 = 96, not 100 — so minor numeric differences between the two outputs are expected and acceptable in practice.

Step-by-Step Worked Examples

Example 1: Infant — 8 kg

Because 8 kg falls in the first tier (≤ 10 kg): 4 × 8 = 32 mL/hr. Using the daily rule: 100 × 8 = 800 mL/day. This applies to healthy term infants and most neonates by actual body weight.

Example 2: Toddler — 15 kg

The first 10 kg contributes 4 × 10 = 40 mL/hr. The remaining 5 kg (in the 10–20 kg tier) contributes 2 × 5 = 10 mL/hr. Total: 40 + 10 = 50 mL/hr. Daily equivalent via 100-50-20: 1,000 + (50 × 5) = 1,250 mL/day.

Example 3: School-age child — 25 kg

First 10 kg: 4 × 10 = 40 mL/hr. Next 10 kg: 2 × 10 = 20 mL/hr. Final 5 kg (above 20 kg): 1 × 5 = 5 mL/hr. Total: 65 mL/hr. Daily via 100-50-20: 1,000 + 500 + (20 × 5) = 1,600 mL/day.

Key Variables Explained

Weight (kg): The child's actual body weight in kilograms. Accurate measurement is critical — a 1 kg error in a 5 kg neonate shifts the rate by 4 mL/hr, representing a 12.5% deviation from the intended target.
Output Rate: Select mL/hr for continuous IV drip orders or mL/day for total daily fluid planning. The calculator applies the correct tiered formula automatically based on the entered weight.

Clinical Scope and Limitations

According to pediatric perioperative fluid management research published in PMC (NIH), the Holliday-Segar formula may overestimate fluid needs in postoperative patients, critically ill children, or patients with syndrome of inappropriate antidiuretic hormone (SIADH) due to non-osmotic ADH stimulation. Conversely, children with fever (estimated 10–12% increase in fluid needs per degree Celsius above 38°C), burns, polyuria, or high gastrointestinal losses may require volumes exceeding the calculated maintenance rate.

The University of Texas Medical Branch Pediatric Education resource on normal maintenance requirements reinforces that these calculated volumes represent a physiologic starting point, not a fixed prescription. Clinicians must individualize therapy using ongoing urine output monitoring (target: 1–2 mL/kg/hr in children; 0.5–1 mL/kg/hr in adolescents), serum electrolytes, and clinical hydration status.

Fluid Type Considerations

Current evidence-based guidelines from major pediatric societies recommend isotonic crystalloids — such as 0.9% normal saline or lactated Ringer's solution — for most hospitalized children requiring IV maintenance fluids. Historical use of hypotonic solutions (e.g., 0.45% NaCl) has been associated with iatrogenic hyponatremia, particularly in postoperative and acutely ill patients where ADH levels are elevated. This calculator provides rate values only; fluid composition must be determined by the treating clinician based on serum sodium, clinical context, and the nature of ongoing losses.

Reference

Frequently asked questions

What is the Holliday-Segar formula and how is it used in the maintenance fluids children calculator?

The Holliday-Segar formula, developed in 1957, calculates pediatric maintenance fluid needs using body weight tiers. It applies 4 mL/kg/hr for the first 10 kg, 2 mL/kg/hr for the next 10 kg, and 1 mL/kg/hr for each kilogram above 20 kg. This maintenance fluids children calculator automates all three tiers instantly, returning either an hourly IV infusion rate or a total daily volume based on the selected output mode.

How do I calculate maintenance fluids for a child weighing 18 kg?

For an 18 kg child using the 4-2-1 rule: the first 10 kg yields 4 × 10 = 40 mL/hr, and the remaining 8 kg in the second tier yields 2 × 8 = 16 mL/hr, for a total of 56 mL/hr. Using the 100-50-20 daily rule: 1,000 mL for the first 10 kg plus 50 × 8 = 400 mL for the next 8 kg, totaling 1,400 mL/day.

What is the difference between the 4-2-1 rule and the 100-50-20 rule for pediatric maintenance fluids?

Both rules derive from the same Holliday-Segar formula but express fluid needs on different time scales. The 4-2-1 rule produces an hourly infusion rate in mL/hr, preferred for writing continuous IV drip orders. The 100-50-20 rule produces a total daily volume in mL/day, suited for fluid planning and oral rehydration. They are clinically interchangeable but not mathematically identical — 4 × 24 = 96, not 100 — so minor numeric discrepancies between the two outputs are normal and expected in clinical use.

When should the standard Holliday-Segar maintenance fluid calculation be adjusted or modified?

The standard formula requires adjustment in several scenarios. Postoperative and critically ill children may need only 50–80% of calculated maintenance due to elevated ADH causing fluid retention. Children with fever require an estimated 10–12% more fluid per degree Celsius above 38°C. Patients with burns, polyuria, or significant gastrointestinal losses need replacement volumes added on top of the calculated maintenance base. Individualize therapy with urine output monitoring, targeting 1–2 mL/kg/hr in children.

Is the Holliday-Segar formula appropriate for neonates and premature infants?

The Holliday-Segar formula was validated primarily for children weighing more than 3–4 kg with mature physiology. Premature infants, neonates under 7 days old, and extremely low birth weight infants have markedly different fluid needs due to immature renal function, increased insensible water loss through thin and permeable skin, and transitional cardiovascular physiology. In these populations, neonatology-specific protocols and continuous metabolic monitoring must guide fluid management rather than the standard 4-2-1 rule.

What fluid type should be paired with the maintenance rate calculated by this tool?

Current guidelines from major pediatric medical societies recommend isotonic crystalloids — specifically 0.9% normal saline or lactated Ringer's solution — as the first-line IV fluid for most hospitalized children. Hypotonic solutions, historically common in pediatric wards, have been linked to hospital-acquired hyponatremia, a serious and preventable complication, especially in postoperative patients with elevated ADH. This calculator provides volume rate only; the treating clinician must select fluid composition based on the patient's serum electrolytes, age, weight, and clinical diagnosis.