Calculating your estimated child dose (clark's rule) is straightforward once you know the Pediatric Dose formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Pediatric Dose Calculator.
What is Pediatric Dose?
The Pediatric Dose calculation tells you your estimated child dose (clark's rule) from a few simple inputs. The figure you are solving for here is the estimated child dose (clark's rule).
The Pediatric Dose formula
The core formula is:
Estimated child dose (Clark's rule) = Adult dose × Child's weight ÷ 70Here is what each input means:
- Adult dose — a value measured in mg. Example: 500 mg.
- Child's weight — a value measured in kg. Example: 20 kg.
How to calculate it step by step
- Write down the adult dose (for example, 500 mg).
- Write down the child's weight (for example, 20 kg).
- Apply the formula above to get your estimated child dose (clark's rule).
- Double-check the result with the Pediatric Dose Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Adult dose | 500 mg |
| Child's weight | 20 kg |
| Estimated child dose (Clark's rule) | 142.9 |
With adult dose of 500 mg and child's weight of 20 kg, the estimated child dose (clark's rule) works out to 142.9.
Example 2
With adult dose of 1,000 mg and child's weight of 20 kg, the estimated child dose (clark's rule) works out to 285.7.
| Result | Value |
|---|---|
| Estimated child dose (Clark's rule) | 285.7 |
Example 3
With adult dose of 250 mg and child's weight of 20 kg, the estimated child dose (clark's rule) works out to 71.4.
| Result | Value |
|---|---|
| Estimated child dose (Clark's rule) | 71.4 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
- These figures are general estimates, not medical advice — check with a qualified professional before acting on them.
Prefer not to do the maths by hand? — the Pediatric Dose Calculator does it instantly, for free, with the formula and a worked example built in.
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