Last updated: 2026-06-22

Pediatric Dose

The pediatric dose calculator converts a weight-based drug order into the three figures used to check it: the milligrams in a single dose, the total milligrams over a day, and the daily maximum for the child. Weight-based dosing — expressed as milligrams of drug per kilogram of body weight (mg/kg) — is the standard approach in pediatrics because children of the same age can differ greatly in size, so a fixed amount cannot be safe across the range. The arithmetic here supports a clinician verifying an order; it is not a substitute for that verification.

Method

A weight-based order has two parts: a per-dose amount in mg/kg and a frequency, the number of doses given per day. The single dose follows directly from the child's weight:

The maximum daily dose uses the drug's published ceiling in mg/kg/day, applied to the same weight:

$\text{max daily} = \text{weight} \times \text{max per kg per day}$

Comparing the planned daily dose against this maximum, as a percentage, shows how much of the ceiling the regimen uses:

$\text{percent of maximum} = \frac{\text{daily dose}}{\text{max daily}} \times 100$

A value at or below 100% stays within the ceiling; above 100% the regimen exceeds it and the order needs review.

Worked example

Consider a child weighing 18.5 kg given an order of 12 mg/kg per dose, three times a day, for a drug with a maximum of 50 mg/kg/day.

Each dose is about 222 mg, the day's total is 666 mg, and that total uses roughly 72% of the 925 mg daily ceiling — within the allowed range, with headroom remaining.

Interpretation and limits

The percent-of-maximum figure is a guard against the most basic error, an order that overshoots the daily ceiling. It does not confirm that the order is correct. Many drugs carry an absolute cap, where the adult maximum becomes the ceiling once a child is large enough, so the mg/kg figure no longer applies at higher weights. Doses are also adjusted for renal and hepatic function, age, the indication being treated, and whether a loading dose differs from the maintenance dose.

This calculator performs the mg/kg arithmetic only and does not consider the product concentration needed to convert a dose in milligrams to a measured volume. Selecting a dose, confirming the maximum, and translating it into an administered amount remain clinical judgments. For related bedside calculations, see the Maintenance Fluids Calculator and Body Surface Area (BSA) Calculator calculators.