How to calculate child dosage

Pediatric Dose Calculator

Created by Łucja Zaborowska, MD, PhD candidate

Reviewed by Bogna Szyk and Steven Wooding

Based on research by

Pan SD, Zhu LL, Chen M, Xia P, Zhou Q. “Weight-based dosing in medication use: what should we know?“ Patient Prefer Adherence (2016)

Last updated: Aug 06, 2022

Table of contents:

How to use the pediatric dose calculator?
Dose frequency abbreviations
How do you calculate pediatric doses?
Child dose calculations examples

The pediatric dose calculator is a simple tool for computing the pediatric dosage for a child of a given weight. 👶

Our calculator allows you to convert values in mg or μg to a precise volume of the medication, using a wide range of units.

The article below is an essential part of our peds dosing calculator - keep on reading to discover all the necessary medical abbreviations, information on pediatric medication dosing, and tips on how to calculate the pediatric dose on your own.

Disclaimer: We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace professional medical advice.

How to use the pediatric dose calculator?

Pediatric dosage is a complicated matter - we can't deny it. We decided to make things easier for you and explain step-by-step all the actions you need to take to receive the most accurate results.

💡 Our mg per kg dosage calculator works both ways; you may convert medication's weight to volume and the other way around.

Decide whether your dose is given in mg or μg.

Milligrams (mg) are 1000 times greater unit than micrograms (μg) - 1 mg = 1000 μg.
Find out your type of dosage.

Your dose in mg/μg might be given:

per kilogram per day (e. g., mg/kg/day) - the most popular option
per kilogram per dose (e.g., mg/kg/dose)
per day (e.g., mg/day)
per dose (e.g., mg/dose)

The calculator will display the chosen dosage type underneath.

Dosage type has a crucial impact on the value of the dosage!
Only the first two types use the dosage calculator by weight; two latter ones rely on a predetermined amount of medication.

Finally, enter your dose amount in mg or μg.

Double-check all the settings - you want to make sure that the pediatric drug dose calculator is computing exactly what you want it to calculate.
Choose the frequency. - check the section below.
Choose the weight of your child and a proper unit.
Enter your drug concentration.

Choose the mass of the drug per given volume of the medication.

The calculator will display the chosen concentration underneath.

💡 Our calculator can also compute the number of tablets needed. To calculate that, enter 1 into the volume field. 💊

Yay! Your results are here - it wasn't that hard, was it? 🎉

If you've already found out everything you need to know, you may as well try and discover our other child dose calculations:

Ibuprofen dosage
Paracetamol dosage calculator
Simple dosage calculator
Epinephrine dose for kids

Dose frequency abbreviations

Dose frequency might be quite misleading since all the abbreviations originate from the Latin language. Here we present a short, useful medical dictionary:

dQ - once per day
BID - twice per day
TID - three times per day
QID - four times per day
q4 hr - once every four hours (6 times per day)
q3 hr - once every three hours (8 times per day)
q2 hr - once every two hours (12 times per day)
q1 hr - once every hour (24 times per day)

How do you calculate pediatric doses?

There's one primary dose calculation formula for children:

▪️ mg/μg per kilogram per day

dose (volume) = (dose (mg/μg) * child's weight) / (concentration * frequency)

where:

concentration is usually given in mg/mL
child's weight is given in kg
frequency means the number of times a chosen medication is given per day. E.g., q1 hr frequency has a value of 24.

However, this equation still has to be modified for every other type of dosage! Below, we enumerated all the available pediatric dosage calculations formulas:

▪️ mg/μg per kilogram per dose

dose (volume) = (dose (mg/μg) * child's weight) / concentration

▪️ mg/μg per day

dose (volume) = dose (mg/μg) / (concentration * frequency)

▪️ mg/μg per day

dose (volume) = dose (mg/μg) / concentration

Hey, how about discovering our other professional pediatric tools:

Maintenance fluids 🚰
Blood volume 💉
Blood transfusion 💉
Growth charts 📈

Child dose calculations examples

Our baby has a fever! 🤒🌡️👶

Still not sure how to calculate pediatric doses? We're going to focus on an mg/kg/day formula since it's the most complex one. Carefully follow the example below:

We bought some paracetamol to lower the fever - its container states that this syrup's concentration is equal to 120 mg /5 mL. Our prescribed peds dose is 10 mg/kg. Our kid's 4.5 years old and weights 20 kg. We need two doses of paracetamol per day.

How much mL of paracetamol syrup do we need per day?

Let's use the following formula:

dose (volume) = (dose (mg/μg) * child's weight) / (concentration * frequency)

First, let's boil down the concentration:

120 mg/5 mL / 5 = 24 mg / 1 mL = 24 mg/mL

Then come back to the equation itself:

dose (volume) = (10 mg/kg * 10 kg) / (24 mg/mL * 2)

dose (volume) = 100 mg / 48 mg/mL

dose (volume) = 2.083 ≈ 2.1 mL - we need 2. 1 mL of paracetamol per dose, twice per day.

Yay, we got it! You're becoming the true pediatric dose master.

Łucja Zaborowska, MD, PhD candidate

Dosage (weight)

Dosage type

mg/kg/day

Frequency

Weight

Drug concentration

Dosage (volume)

Dosage

per dose

per 24h

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Young's Rule - StatPearls - NCBI Bookshelf

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.

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Christian I. Wade; Thirsa Martinez.

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Last Update: February 17, 2022.

Definition/Introduction

Young's Rule is an equation used to calculate pediatric medication dosage based on the patient's age and the known recommended adult dose. The definition of Young's Rule is the age of the patient, divided by the age added to twelve, all multiplied by the recommended adult dose. This formula appears below:

[Age / (Age + 12)] x Recommended Adult Dose = Pediatric Dose

Young's Rule can be applied to quickly approach a situation in which the patient's weight is unknown. Other approaches to pediatric dosing that also use age include Webster's Rule and Fried's Rule.

If the weight of the patient is known, Clark's Rule or the Body Surface Area rule can be implemented.[1]

Issues of Concern

Pediatric dosing based on one's age has the potential for suboptimal therapeutic levels due to the broad range of potential weight, especially with increasing childhood obesity.[2][3]

Clinical Significance

In situations where the pediatric patient's weight is unknown, for instance, at the point of injury, then Young's Rule can be safely implemented if their age and the recommended adult dosing are known. Additionally, certain classes of medications require weight-based dosing, such as antibiotics and antiepileptics. Ultimately, age-based dosing has been demonstrated to be a safe and effective approach. However, caution should be used depending on the class of the drug.[4][5]

Nursing, Allied Health, and Interprofessional Team Interventions

Knowledge of Young's RUle can serve several purposes in pediatric drug dosing, and members of the interprofessional healthcare team would do well to be familiar with the rule. The most obvious use is for the clinician when calculating the dose for a pediatric patient. A secondary use can be to verify that the dose ordered or prescribed is not outside of the parameters for the child. This is where nurses, during administration or pharmacists, when filling an order or prescription, can apply the rule and potentially stop a toxic dose or a therapeutically insufficient dose. In an open, interprofessional team environment, this can improve patient outcomes and prevent adverse events. [Level 5]

Review Questions

Access free multiple choice questions on this topic.
Comment on this article.

References

1.: Delgado BJ, Safadi AO, Bajaj T. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 5, 2022. Clark's Rule. [PubMed: 31082148]
2.: Ogden CL, Carroll MD, Lawman HG, Fryar CD, Kruszon-Moran D, Kit BK, Flegal KM. Trends in Obesity Prevalence Among Children and Adolescents in the United States, 1988-1994 Through 2013-2014. JAMA. 2016 Jun 07;315(21):2292-9. [PMC free article: PMC6361521] [PubMed: 27272581]
3.: Kendrick JG, Carr RR, Ensom MH. Pharmacokinetics and drug dosing in obese children. J Pediatr Pharmacol Ther. 2010 Apr;15(2):94-109. [PMC free article: PMC3018176] [PubMed: 22477800]
4.: Elias GP, Antoniali C, Mariano RC. Comparative study of rules employed for calculation of pediatric drug dosage. J Appl Oral Sci. 2005 Jun;13(2):114-9. [PubMed: 20924533]
5.: Kendrick JG, Carr RR, Ensom MH. Pediatric Obesity: Pharmacokinetics and Implications for Drug Dosing. Clin Ther. 2015 Sep 01;37(9):1897-923. [PubMed: 26361823]

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

Bookshelf ID: NBK554603PMID: 32119490

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Calculation of the dose of a medicinal substance for a child.

Calculation of the dose of a medicinal substance for a child.

: Acidberry10; June 5th, 2013

Current Location:: In the same place, where

9000 9000 9000 9000 Current Mood:

9000

004

dissatisfied

Current Music:: silence

I'm lucky
(c) Yandex

I know that among my readers there are several people who graduated from the medical faculty, but who want to go to pediatrics. Especially for them, I would like to provide information on the calculation of doses for children. Perhaps this information will also give food for thought to adult doctors who do not understand that in body weights of 50 kg and 100 kg, a dose of 15 mg of some Pentaxicillin will be distributed differently. And you yourself know about such features of the body as kidney, liver failure, individual characteristics of detoxification systems and the binding of drugs to albumins :). nine0040

State Pharmacopoeia (Edition X) recommends calculation based on the age of the child. The adult dose is taken as a unit, the children's unit is a part of this dose:

children up to a year 1/24-1/12,
2 years old - 1/8,
4 years old - 1/6,
6 years - 1/4,
7 years - 1/3,
14 years - 1/2,
15-16 years - 3/4.
This method of calculation is not accurate enough, since the weight of children of the same age may vary

According to Young's rule, the children's dose is determined as follows

where Fd is the children's dosage (filii dosis), Ad is the adult dosage (adult dosis) A is the age (anno). The formula is actually written in Russian letters, but since I'm dibilko, and I don't know how to use an online editor for formulas, I had to pervert inventing the letter designation of the variable.

according to Clark's rule, the calculation is as follows

Where m is the body weight in kg (of the same ones) on which the medicinal substance will act. nine0039 For ease of calculation, I would like to provide a

calculator

A more perfect calculation of the child dose using the Fd factor: the adult dose is recalculated per 1 kg of body weight by dividing by 70, then multiplied by the child's body weight and by Fd.

Age	up to 1 year	1-6 years old	6-10 years	10-12 years	13-15 years old
Fd	1.8	1.6	1.4	1.2	1. 1 or 1.0*

*if the weight and height of the child's body are close to those of adult family members.

Determining the dose of the drug by body surface area.

Body weight, kg	Estimated age	Body surface area, m2	percentage of the average single (daily) adult dose
3	newborn	0.2	12
6	3 months	0.3	18
10	1 year	0.45	28
20	5.5 years old	0.8	48
30	9 years	1	60
40	12 years old	1.3	78
50	14 years old	1. 5	90
60	adult	1.7	102
70	adult	1.76	103

nine0000 Children's dosage: measure correctly - Letidor

Despite the fact that the dosages are indicated in the instructions for the drug, the question: "How to calculate the amount of medicine for a child?" - I hear it very often. And this is good. It is much worse if the mother does not think about it and gives the baby an extra second or even third pill to enhance the effect.

But even if parents understand the meaning of children's dosage, they do not always know the practical details. For example, not all tablets can be cut in half, and not all teaspoons are equally useful in measuring five milliliters. nine0040

Limits of the norm

There are two main doses for any drug:

Maximum single dose - how much you can drink at one time
Maximum daily is the total amount of medication per day.

They are especially important for over-the-counter products, the instructions for which parents rarely read, considering them harmless. Which is not true at all. These doses should not be exceeded in any case, the consequences can be varied, but always unpleasant, sometimes even downright dangerous. From the instructions, you can generally learn a lot of interesting things, for example, that acetylsalicylic acid should not be given to children under 12 years old. nine0040

Under 16 and over

Children's doses are calculated based on body weight. Age also matters, but if a too well-developed girl weighs 40 kg at 10 years old, she will need the same amount of the drug as a 15-year-old asthenic boy with the same weight. That is why all instructions indicate not only the age, but also the weight category of the child.

Example: Maximum daily doses of paracetamol (do not forget to count ALL paracetamol included in hot drinks, syrups, suppositories, etc. ). nine0040

up to 6 months (up to 7 kg) - 350 mg
from 6 months to a year (up to 10 kg) - 500 mg
1-3 years (up to 15 kg) - 750 mg
up to 22 kg) — 1 g
6–9 years (up to 30 kg) — 1.5 g
9–12 years (up to 40 kg) — 2 g

Important! There are no universal rules for calculating the dose that could guarantee the effectiveness and safety of the use of drugs in children, especially newborns. The pediatrician should correctly prescribe the drug. nine0263

Indivisible whole
Many people think that it is enough to split a tablet in half and the required dosage will be observed! You can break it only if there is a special groove. In other cases, special medicines with multiple doses are required. Why is it so?

Firstly, during production it is almost impossible to mix the mass to a homogeneous state and make sure that exactly 50% of the necessary ingredients are in the half. Studies have shown that this percentage ranges from 20 to 80. And the spread of dosages will be the higher, the more components in the drug. nine0040
Secondly, in addition to the main active ingredient in the tablet, there is also a lot of auxiliary, added not at all in a 1:1 ratio. And when dividing them, it will turn out less than what is required for the correct "work" of the medicine.

_ Important! Never replace "baby" doses with half or quarter "adult" doses. This is fraught with an overdose, especially in young children. _

A spoon for mother
Liquid dosage forms are sometimes measured incorrectly. Most people are sure that a teaspoon is 5 ml, a dessert spoon is 10 ml, and a tablespoon is 15 ml. But firstly, there are tablespoons and 20 ml each, and teaspoons - 7.5 ml each. Secondly, not everyone fills even a standard spoon exactly to the brim. nine0040
American scientists from Cornell University conducted a study, and it turned out that when using medium-sized spoons, patients receive 8. 4% less of the drug, and 11.6% more when measuring the remedy with large spoons. At the same time, every fifth participant in the experiment was sure that in both cases the medicine would give the same effect.

The consequences of a single over- or underdose are negligible, but for people forced to take the medicine every 4-8 hours for several days, this difference between the recommended and actual dose can be significant. nine0040
_ Important! Use cutlery only if the medicine does not come with a special measuring container - a cap or a spoon. _

Herbs for the baby
The most difficult situation is with the use of medicinal plants in children. Unfortunately, the recommendations on the packages, as a rule, apply only to adult patients. Many mothers brew herbs for a child “as written on the pack”, that is, an adult dose, and at the same time receive an overdose of a medicinal substance, which can result in allergic, toxic reactions, and deterioration in well-being. But the herbs will be completely innocent! So that they give only strength and health, we present the most commonly used children's dosages. nine0040
Dosages of herbs and herbs (based on 2 days):
4-5 years - 0.5 l dessert spoon

6-7 years - 0.5 l tablespoon

- 8-10 years - 0.5 l heaping tablespoon

11 -12 years - 1.5 tablespoons per 0.5 l

13-15 years - 2 tablespoons per 0.5 l

immediately for 2 days. Store it in the refrigerator and warm up to room temperature before use. nine0040
The child should drink half of the prepared dose per day (about a glass on average). Divide it into 3-5 doses. Up to 3 years old - from 1 to 3 tablespoons per dose, over 3 years old - about 1/3 cup.

It is desirable to vary the daily dose depending on the constitution and weight of the children. For thin people, we reduce it by about 1/5. We increase the "dumplings" by the same amount. Usually these variations come down to the presence or absence of a slide in a spoonful of dry grass. If you use medicinal plants and fees in filter bags, be guided by such children's dosages (based on 2 days):

Restrictions on the use of herbs in children of the first year of life are mainly due to the immaturity of most enzyme systems. They are not always able to provide an adequate response to the entry of new chemicals into the body, therefore, an allergic or toxic reaction may develop, explains _ Olga DANILYUK , phytotherapeutist, candidate of medical sciences, assistant of the Department of Phytotherapy of the FPCMR PFUR._

For example, the younger the baby , the higher the risk of toxic effects of peppermint and menthol essential oils on the central nervous system. With their overdose, convulsions and vomiting are possible, especially in children of the first 6 months of life. Mint is not prescribed for children of the first year of life. With age, the threat of poisoning with peppermint oils or menthol decreases markedly, and after 3 years there is no danger anymore.
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