Pediatric Maintenance Fluids Calculator

Maintenance fluids are the baseline volume of intravenous fluid estimated to replace a child's normal ongoing losses — urine, stool, and insensible losses from the skin and lungs — over 24 hours when the child cannot meet those needs by mouth. They keep a stable, euvolemic child in fluid balance; they are not intended to correct an existing fluid deficit. This is an educational estimate — any real fluid plan must be verified with a pediatrician or pharmacist.

The Holliday-Segar method, from Holliday and Segar's 1957 paper, estimates daily maintenance fluid as 100 mL/kg/day for the first 10 kg of body weight, plus 50 mL/kg/day for the next 10 kg (11–20 kg), plus 20 mL/kg/day for each kilogram above 20 kg. For example, a 26 kg child: (10 × 100) + (10 × 50) + (6 × 20) = 1000 + 500 + 120 = 1620 mL/day.

The 4-2-1 rule estimates the hourly maintenance infusion rate: 4 mL/kg/hour for the first 10 kg of body weight, plus 2 mL/kg/hour for the next 10 kg (11–20 kg), plus 1 mL/kg/hour for each kilogram above 20 kg. For a 26 kg child: (10 × 4) + (10 × 2) + (6 × 1) = 40 + 20 + 6 = 66 mL/hour.

The 4-2-1 tiers (4, 2, 1) are the Holliday-Segar daily tiers (100, 50, 20) divided by 24 and rounded to whole numbers (100/24 ≈ 4.17, 50/24 ≈ 2.08, 20/24 ≈ 0.83). Because of that rounding, the two answers agree closely but not exactly — for a 26 kg child, 1620 ÷ 24 = 67.5 mL/hour versus 66 mL/hour by the 4-2-1 rule. The small difference is expected; both are approximations of the same method.

The calculator accepts 3.5 kg to 100 kg. The Holliday-Segar method does not apply to neonates (under 28 days of age) or infants below about 3.5 kg, who need specialized neonatal fluid protocols managed by a neonatologist. Above 65 kg the result is held at the common clinical ceiling of 2400 mL/day (105 mL/hour); larger patients are usually managed with adult fluid guidance — discuss with a clinician.

Holding maintenance fluids at 2400 mL/day (105 mL/hour) above roughly 65 kg is a common clinical convention to avoid excessive volumes in larger patients. It is a convention, not part of Holliday and Segar's original 1957 nomogram. This calculator applies the cap and labels it clearly; whether a cap is appropriate for a specific patient is a clinical decision.

Many clinicians use ideal or adjusted body weight rather than actual weight when a child has obesity, because adipose tissue is less metabolically active and dosing on actual weight can overestimate fluid needs. There is no single universally agreed formula, so this is a decision to make with the treating clinician or pharmacist — this calculator uses the weight you enter.

A fluid bolus — commonly 20 mL/kg of isotonic crystalloid, often capped at 1000 mL — is given rapidly (over minutes) to treat signs of poor perfusion or dehydration, which is different from slow 24-hour maintenance fluids. This calculator shows the 20 mL/kg reference figure for context only; it does not estimate fluid deficits or replace clinical assessment.

No. The Holliday-Segar and 4-2-1 rules estimate baseline maintenance only. A child who is dehydrated needs an estimated deficit plus replacement of ongoing abnormal losses (vomiting, diarrhea, fever, drainage) in addition to maintenance. This calculator does not compute deficits — it provides the maintenance baseline that a full fluid plan is built on.

Yes, it is free, needs no account, and runs entirely in your browser. But it is an educational aid, not medical advice: every real IV fluid order needs an independent double-check against the child's clinical status, institutional policy, and a pediatrician or pharmacist before anything is administered.