The maintenance fluids calculator uses the Holliday-Segar method and the 4-2-1 rule to determine the daily and hourly need for fluids in children. As well as finding out these pediatric maintenance fluids, you can also work out the proper size of the pediatric fluid bolus to be given in times of need.

We try our best here at Omni to make our calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. Before administering any drug, fluid, blood or treatment to your kid patient, make sure you know the correct dose and method.

How to use pediatric maintenance fluids calculator?

  1. Determine if you should use the maintenance fluids calculator, as the formula used here has its limitations. You should not use it for newborns under 14 days old, as it overestimates the fluids needed. Also, the formula is not suitable for children under 3 kilograms. The calculator will warn you about that.
  2. Input child's weight. Consider using the ideal body weight in obese patients.
  3. You will get three results. The first is daily maintenance fluids - the fluid need for the whole day - to be given in 24 hours.
  4. In the next line, you'll see Fluids flow rate. It tells you how fast the intravenous infusion should be.
  5. The last line informs you about the pediatric fluid bolus amount. Check the section below to find out more.

Holliday-Segar method and 4-2-1 rule

The formula used in our maintenance fluid calculator is an old, well-established method, called after 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. The modification of this principle, called 4-2-1 rule, gives you a similar answer, but per hour. See the summary of both rules below.

weight Holliday-Segars rule 4-2-1 rule
first 10 kg (3-10 kg) 100 ml/kg/24h 4 ml/kg/h
next 10 kg (11-20 kg) 50 ml/kg/24h 2 ml/kg/h
above 20 kg 20 ml/kg/24h 1 ml/kg/h

Are you using imperial units? Don't worry! The maintenance fluids calculator can easily convert between any units with its built-in weight converter.

Please note that in obese patient you should think about using the ideal body weight. The best way to monitor a child's weight and weight to height ratio is to check how they behave in percentile ranges. Try our BMI percentile calculator for that, and take a look at the growth charts for any height concerns.

Let's have an example to keep everything clear. How much fluid would a child of 14 kg 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

A term 'bolus' means an intravenous dose of a drug given relatively quickly, and very often directly from hand. A bolus is often used in acute states, when there is a need for the drug to reach the desired place (e.g., heart in case of resuscitation) and act as fast as possible.

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

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

bolus fluids = weight (kg) * 20 ml

with the maximum limit of 1000 milliliters = 1 liter.

This amount should be given as fast as possible - as shock is a direct life-threatening state.

Aleksandra Zając, MD

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Maintenance Fluids Calculator | 4-2-1 Rule