How To Calculate Supplement Dosages For Kids

A mother pours a supplement into a small cup for the child sitting on her lap.

Ensuring your child receives the right supplement dose is crucial for their optimal health and well-being.

As a parent, you want nothing but the best for your children’s health and wellbeing. Whether it's ensuring they receive a balanced diet or providing them with essential vitamins and minerals, you are on it! However, it can be a bit perplexing when calculating supplement doses for your little ones.


In this article, we’ll discuss the importance of accurate supplement dosing for kids and explain both Clark's Rule (based on the child’s weight) and Young's Rule (based on the child’s age) as methods of calculating doses. We’ll also touch on the importance of taking a comprehensive approach to calculating doses, why children might need relatively higher doses for some vitamins than adults, and how to take that into account when calculating their supplement doses.

The Importance of Accurate Dosing For Kids

Before getting into the nitty-gritty of dose calculation methods, it is necessary to talk about the importance of calculating the correct dose, especially for kids. 

Children, with their rapid growth and development, have high nutritional needs. Children are not mini-adults, and each child is unique due to factors such as dietary intake, level of physical activity, amount of mental stress, time spent outdoors, and even genetic single nucleotide polymorphisms (SNPs). 

When calculating supplement doses for kids using the rules below, it’s also imperative to consider their age group’s recommended daily intake (RDI), personal dietary intake, and individual lifestyle factors to ensure correct dosing.

Two Rules For Calculating Supplement Doses For Kids

Clark's Rule and Young's Rule are commonly used to calculate supplement doses for kids.

Clark's Rule: Based On Weight


Clark's Rule is a dosage calculation method that takes your child's weight into account (1). This rule can be used to calculate doses for kids ages 2-17. This formula adjusts the adult dosage proportionally to your child's weight.


Here's how it works:

To use Clark's Rule, you will need your child's current weight and the recommended adult dosage, which can usually be found on a supplement’s product label. This calculation can be done in either kilograms or pounds. I use pounds in the formula below.


To calculate a child's dosage using Clark’s Rule, use the following formula:


Child's Dosage = (Child's Weight in lb / 150 lb) x Adult Dosage

A boy stands on a scale while his dad brushed his teeth  behind him.

Young's Rule: Based On Age


Young's Rule takes into account your child's age rather than the child’s weight (2). This rule can be used to calculate doses for kids ages 2-17.


Here's how it works:

To use Young’s Rule, you will need the recommended adult dosage and your child’s age in years.


To calculate the child's dosage using Young’s Rule, use the following formula:


Child's Dosage = (Child's Age / (Child's Age + 12)) x Adult Dosage

Two girls playing with wooden toys.

Practical Examples

Let's put Clark's Rule and Young's Rule into action with practical examples to illustrate how these methods work in real-life scenarios.

Practical Example 1: Clark's Rule


Scenario: You have a 9 year old child who weighs 63 pounds, and you need to determine the correct dosage for a supplement recommended for adults at 500 milligrams.

Determine your child's weight in pounds: 63 lbs. 

Use Clark's Rule: (Child's Weight in pounds / 150) × Adult Dosage

Calculate: (63 / 150) × 500 milligrams


The result is 210 milligrams.

Practical Example 2: Young's Rule


Scenario: You have a 9 year old child who weighs 63 pounds, and you need to determine the correct dosage for a supplement recommended for adults at 500 milligrams.

Determine your child's age in years: 9 years

Use Young's Rule: (Child's Age in years / (Child's Age in years + 12)) × Adult Dosage

Calculate: (9 / (9 + 12)) × 500 milligrams


The result is 214 milligrams.



As you can see, both Clark’s Rule and Young’s Rule give similar dosage results. However, we need to look at the child holistically, which includes considering their dietary intake as well as the RDI (recommended daily intake) and the UL (upper limit) for the nutrient in question.

A young girl smiles while eating food.

The Recommended Daily Intake

When deciding on a supplement for your child, it is important to look at several factors, including the RDI (recommended daily intake) for the nutrient* you are considering supplementing. Although Clark’s Rule and Young’s Rule are helpful guidelines for most nutrients, they do not take into account that children’s organ systems are different than adults’ and there are certain nutrients of which children need relatively higher amounts than adults (1).

For some nutrients, the amount children need is proportional to the amount adults need. For others, the RDI for a child might be the same as or even exceed that of an adult. For example, the RDI of calcium for 9-18 year olds exceeds that of an adult aged 19-50 (3). In the case of calcium supplementation, if we only applied Young’s Rule without looking at the RDI, it would lead us to supplement a child with 214 mg per day, which would be too low for a child who needs between 1300 and 3000 mg of calcium per day.

*Unlike vitamins and minerals, herbs often do not have a universally recommended dosage for children. Perhaps the most useful application of Clark’s Rule and Young’s Rule is when calculating doses of herbal supplements.

Safe & Effective Supplement Use

Both Clark's Rule and Young's Rule offer valuable guidance for calculating supplement doses for children. It is important to take a birds eye view of your child’s health by looking at all the relevant factors when determining a dose, including the way your child responds to a supplement, other supplements or medications they may already be taking, average dietary intake, symptoms, lifestyle, blood work, and more. Taking this approach allows us to prevent deficiency while also preventing toxicity.


Ensuring your child receives the right supplement dose is crucial for their optimal health and well-being. Children have unique nutritional needs influenced by various factors like diet, physical activity, stress levels, genetics, and more. Time-tested dosing methods like Clark's Rule and Young's Rule, which account for weight and age respectively, provide valuable guidance for supplement dosage calculations. However, it's essential to take into account the recommended daily intake (RDI) for specific nutrients. Holistically assessing your child's health, monitoring their responses to supplements, and consulting healthcare professionals when necessary are essential steps to ensure safe and effective supplement use.


1. Delgado, B. J., Safadi, A. O., & Bajaj, T. (2021). Clark’s Rule. PubMed; StatPearls Publishing.


2. Wade, C. I., & Martinez, T. (2022). Young’s Rule. PubMed; StatPearls Publishing.


3. National Institutes of Health. (2019, December 6). Office of Dietary Supplements - Calcium.

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