Pediatric Fluid Maintenance Calculator
Calculates a child's daily maintenance fluid requirement using the Holliday-Segar method based on body weight. Commonly used by nurses and physicians when prescribing IV fluids or assessing baseline hydration needs.
Last updated: May 2026
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About this calculator
The Holliday-Segar method, published in Pediatrics in 1957, is the standard approach to estimating daily maintenance fluid needs in children. It uses a three-tier weight-based formula: for the first 10 kg of body weight, allow 100 mL/kg/day; for the next 10 kg (weights 10–20 kg), add 50 mL/kg/day for that segment; for every kilogram above 20 kg, add 20 mL/kg/day. Expressed as a piecewise formula: if weight ≤ 10 kg, fluids = weight × 100; if weight ≤ 20 kg, fluids = 1,000 + (weight − 10) × 50; if weight > 20 kg, fluids = 1,500 + (weight − 20) × 20. Variables: weight (in kg). These estimates reflect baseline insensible losses (skin and respiratory), normal urine output, and metabolic water needs derived from caloric expenditure. The same calculation produces an hourly rate via the '4-2-1 rule': 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for weights 10–20 kg, and 1 mL/kg/h for each kg above 20 kg. Edge cases: this formula provides maintenance only — it does not include replacement of pre-existing deficits (e.g., from gastroenteritis dehydration) or ongoing losses (vomiting, diarrhea, fistula output, burns, NG drainage). Fever increases insensible losses by approximately 10–12% per °C above 38°C and requires upward adjustment. Conversely, conditions like SIADH, acute kidney injury, congestive heart failure, post-craniotomy, and meningitis often require fluid restriction (typically 60–80% of calculated maintenance) to reduce risk of dilutional hyponatremia and cerebral edema. Maintenance fluids in modern practice should be isotonic (0.9% saline or balanced crystalloid like PlasmaLyte) — hypotonic fluids are no longer first-line because of hyponatremia risk (NICE/ESPNIC 2015 guidance).
How to use
Example 1: A child weighs 25 kg. Step 1: weight > 20 kg, so use the third tier. Step 2: fluids = 1,500 + (25 − 20) × 20 = 1,500 + 100 = 1,600 mL/day. Step 3: hourly rate = 1,600 / 24 ≈ 66.7 mL/hour. Verify by the 4-2-1 rule: (10 × 4) + (10 × 2) + (5 × 1) = 40 + 20 + 5 = 65 mL/hour — within rounding agreement. Example 2: A 7 kg infant. Step 1: weight ≤ 10 kg, so first tier. Step 2: fluids = 7 × 100 = 700 mL/day. Step 3: hourly rate = 700 / 24 ≈ 29 mL/hour. Verify by 4-2-1 rule: 7 × 4 = 28 mL/hour — matches. Note: these figures are maintenance only and do not include deficit replacement for a dehydrated child or ongoing-loss replacement for ongoing diarrhea/vomiting.
Frequently asked questions
What is the Holliday-Segar method for calculating pediatric fluid maintenance?
The Holliday-Segar method is a weight-based formula developed by Holliday and Segar in 1957 that estimates a child's daily maintenance fluid requirements by dividing body weight into three segments. The first 10 kg accounts for 100 mL/kg/day, the second 10 kg (weights 10–20 kg) accounts for 50 mL/kg/day, and any weight above 20 kg accounts for 20 mL/kg/day. These tiers reflect decreasing metabolic water needs per unit of body mass as body size increases (caloric expenditure per kg decreases with size). The method is universally taught in medical and nursing training and remains the most commonly used bedside tool for initial IV fluid prescribing in children worldwide. Modern guidance (NICE 2015, ESPNIC 2018) reaffirms its calculation but now recommends isotonic rather than hypotonic fluid composition to reduce hyponatremia risk.
When should pediatric maintenance fluids be adjusted above or below the calculated amount?
The Holliday-Segar calculation is a baseline that must be modified in many clinical situations. Fever increases insensible water losses by roughly 10–12% per °C above 38°C, so febrile children often need 10–25% more fluid. Hot environments, burns, and tachypnea also increase losses. Conversely, children with conditions such as syndrome of inappropriate antidiuretic hormone secretion (SIADH), acute kidney injury, congestive heart failure, post-cranial surgery, or meningitis often need fluid restriction (60–80% of maintenance) to reduce hyponatremia and cerebral edema risks. Children with ongoing GI losses (diarrhea, vomiting, NG drainage, ileostomy output) need volume-for-volume replacement on top of maintenance. Dehydrated children also need deficit replacement (typically over 24–48 hours) added to their maintenance plan. Always reassess fluid balance with daily weights, intake/output, urine output, and serum sodium.
How do I convert a daily pediatric fluid maintenance volume to an hourly IV drip rate?
Divide the total daily maintenance volume in milliliters by 24 to obtain the hourly infusion rate. For example, if the daily requirement is 1,600 mL, the hourly rate is 1,600 ÷ 24 ≈ 67 mL/hour. A useful shortcut taught in pediatric training is the '4-2-1 rule': 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the next 10 kg (weights 10–20 kg), and 1 mL/kg/h for each kg above 20 kg. This produces the same result as the daily Holliday-Segar calculation divided by 24, within rounding. For a 25 kg child: (10×4) + (10×2) + (5×1) = 40 + 20 + 5 = 65 mL/h, matching ~1,600 mL/day ÷ 24. Always set infusion pumps accurately, double-check the rate at each shift change, and reassess as the child's clinical condition changes.
What are common mistakes when prescribing pediatric maintenance fluids?
Using hypotonic fluids (0.45% saline, D5W, or 0.18% saline) for maintenance — modern guidance recommends isotonic (0.9% saline or balanced crystalloid) because hypotonic fluids cause iatrogenic hyponatremia, which can be fatal. Forgetting to add ongoing-loss replacement on top of maintenance for diarrhea, vomiting, or NG output. Forgetting to add deficit-replacement volumes for already-dehydrated children. Continuing maintenance fluid rates after enteral nutrition is restarted, leading to fluid overload. Not adjusting downward for children on fluid restriction (SIADH, head injury, heart failure). Calculating using estimated rather than measured weight. Confusing daily volume with hourly rate (a factor-of-24 error is catastrophic). Using adult fluid rates (often 80–125 mL/h) for children whose true need may be only 20–60 mL/h. Failing to monitor electrolytes during prolonged IV fluid therapy — sodium, potassium, glucose, and urea/creatinine should be checked at least daily. Finally, not reassessing the need for IV fluids — many children can transition to oral or NG fluids within hours.
When should I NOT use the Holliday-Segar formula?
Neonates (under 28 days) need specialized neonatal fluid prescriptions — Holliday-Segar significantly underestimates their needs in the first days of life (when fluid requirements start at 60–80 mL/kg/day on day 1 and progressively increase). Premature infants need bespoke neonatal-intensive-care fluid plans. Children with significant fluid restrictions (SIADH, severe heart failure, acute renal failure) need restricted, not maintenance, volumes — typically 60–80% of Holliday-Segar. Burn patients need Parkland formula for the first 24–48 hours, then maintenance plus ongoing burn-evaporative losses. Diabetic ketoacidosis requires a specific fluid protocol with controlled rates to avoid cerebral edema — not Holliday-Segar. Surgical patients with major third-space losses (e.g., intestinal surgery) need adjusted plans. Children on enteral or parenteral nutrition with fluid included in feeds need that subtracted from the IV maintenance order. Children with congenital heart disease and single-ventricle physiology have specific perioperative fluid limits. For any of these scenarios, use disease-specific protocols and consult the pediatric intensive care or specialist team.