Get to know the 4 2 1 fluid rule

The Maintenance Fluid Calculator (MIVF Calculator) uses the Holliday-Segar method and the 4 2 1 fluid rule to determine children’s daily and hourly fluid needs. In addition to knowing these pediatric maintenance fluids, you can also calculate the appropriate size of pediatric fluid bolus to give in times of need.

How to use the pediatric maintenance fluid calculator?

  1. Determine if you should use the maintenance fluid calculator, as the formula used here has its limitations. You should not use it for newborns under 14 days, as it overestimates the necessary fluids. Also, the formula is not suitable for children under 3 kilograms. The calculator will warn you about that.
  2. Enter the child’s weight. Consider using the ideal body weight and ideal weight calculator in obese patients.
  3. You will get three results. The first is daily maintenance fluids, fluids needed for the entire day, to be administered within 24 hours.
  4. On the next line, you will see the fluid flow rate. It tells you how fast the intravenous infusion should be.
  5. The last line tells you about the amount of the pediatric fluid bolus. 

Holliday-Segar Method and 4-2-1 Rule

The formula used in our IVFM calculator is an old and well-established method, named for its developers, pediatricians Malcolm Holliday and William Segar.

The assumption that allows this formula to work is that a fixed amount of fluid is needed for every kilogram per day. Modifying this principle, called the 4-2-1 rule, gives you a similar answer, but per hour.

Are you using imperial units? Don’t worry! Built-in weight converter.

Please note that in obese patients you should consider using the ideal body weight. The best way to monitor a child’s weight and weight-to-height ratio is to see how they perform across percentile ranges. 

How to use the MIVF calculator – practical example

Let’s give an example to make everything clear. How much fluid would a 14 kg child need?

  1. For 24 hours – Holliday-Segar method
    first 10 kg * 100 ml/kg/24h + next 4 kg * 50 ml/kg/24h = 1200 ml/24h
  2. For one hour – 4-2-1 rule
    first 10 kg * 4 ml /kg/24h + next 4 kg * 2 ml/kg/24h = 48 ml/24h

The answer: the amount of daily pediatric maintenance fluids is 1200 ml, and the hourly demand is 48 ml.

Pediatric fluid bolus

The term “bolus” means an intravenous dose of a drug that is given relatively quickly and very often directly from the hand. A bolus is often used in acute states when there is a need for the drug to reach the desired site (eg, the heart in case of resuscitation) and act as quickly as possible.

A bolus of fluid is given to rapidly fill the vascular bed and is given primarily in the presence of hypovolemic shock.

In children, the amount of fluid given as a bolus can be calculated using the formula:

fluid bolus = weight (kg) * 20 ml

with an upper limit of 1000 ml = 1 litre.

This amount should be administered as quickly as possible, since shock is a directly life-threatening condition.


One of the main objectives of maintenance parenteral fluid therapy is to provide water to cover physiological losses (insensible loss + urine loss). In a study published in 1957 in the Journal Pediatrics, Malcolm Holliday and William Segar developed a simple scheme that could be easily remembered to calculate maintenance water needs for hospitalized patients.

Assimilating the physiology known at that time, they observed that “there was a DIRECT LINEAR relationship between Physiological Water Needs (insensible losses + urinary losses) and Energetic Metabolism”. In other words, “the average water needs, expressed in milliliters, are equivalent to energy expenditure in calories (under normal resting conditions, 1 ml of water is needed to metabolize 1 kcal)”. It was found that the relationship between Weight and Energy 

Expenditure is NONLINEAR. Based on their data and assumptions, Holliday and Segar constructed a curve that plotted caloric energy needs versus weight. This curve could be seen composed of three linear sections that coincided approximately with the following weight sections: 0 to 10 kg, 10 to 20 kg and 20 to 70 kg.

Viewed this way, the authors concluded that 100 mL/kg/day for weights up to 10 kg, an additional 50 mL/kg/day for each kilogram from 11 to 20 kg, and an additional 20 mL/kg/day for each kilogram above 20 kilos In anesthetic practice, this formula has been further simplified, with the hourly requirement known as the “4-2-1 rule” (4 ml/kg/h for the first 10 kg of weight, 2 ml/kg/ h for the first 10 kg). next 10 kg and 1 mL/kg/hr for each kilogram thereafter.

 Volume Calculations

  • All fluids should be calculated as maintenance + deficit correction + ongoing losses (
  • maintenance Fluid requirements of 1ml/kg/hr thereafter, with a maximum maintenance of 100ml/hr). See the RCH IV Fluid CPG and Maintenance Fluid Calculator.
  • Correctors can be calculated according to the RCH guidelines for gastroenteritis. Make sure IVs if looking at RCH CPG, not Fluid nasogastric rates

Types and Options

All pediatric IV fluids at BHS are based on and comply with the Standards for Pediatric Fluids: NSW Health (2nd Edition).

An excellent IV fluid types and volumes review article is available: McNab JPCH 2016.

Premixed IV fluid bags should be used in almost all circumstances for pediatric patients at BHS. 

note that there is emerging evidence for the use of Plasma-Lyte 148 in maintenance and replacement fluids, although this is not yet supported as standard practice.

hyponatremic fluids such as 0.225%, 0.22%, or 0.18% NaCal (1/5) Should be avoided unless in consultation with a consulting pediatrician (other than neonates as noted above).

dextrose to be addedAll newborns should receive 10% dextrose and all other children should receive 5% dextrose (plus additives) at all times, unless otherwise specified by the Pediatric Unit.

  • Pediatric patients fasting for the operating room and other situations still require dextrose.

Fluid Boluses

  • All fluid boluses for volume should be administered with normal saline (0.9% NaCl), even in
    • neonates
  • . used for correction of hypoglycaemia
  • Colloids should be avoided for fluid boluses in children
  • Aggressive fluid boluses, even in sepsis, can cause harm and should be performed with caution
    • IV fluid resuscitation therapy, Long JPCH 2016

Enteral Fluids

  • Please note that nasogastric fluids are delivered at different rates and we use different types of fluids.
    • NGT fluid rates can be calculated using RCH gastroenteritis CPG
    • NGT fluids for rehydration/hydration are ORS or breast milk/artificial formula.
    • Never give fluids intravenously
  • through a nasogastric tube. to all enteral fluid orders (other than IV fluid chart)
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