How is a weight-based dose calculated?

The single dose equals the child's weight in kilograms multiplied by the drug's mg/kg-per-dose figure. The daily total multiplies that by the number of doses per day. A maximum per-dose ceiling caps the result for heavier children.

Why is there a maximum dose ceiling?

Above a certain weight a mg/kg dose would exceed the safe adult dose, so most drugs have an absolute per-dose cap. The tool applies that cap automatically and warns you when the calculated dose is capped, so a large child is never overdosed.

Which drugs are included as presets?

Common pediatric agents: paracetamol, ibuprofen, standard and high-dose amoxicillin, azithromycin, and cefalexin, each with typical mg/kg, frequency, and a per-dose ceiling. A custom option lets you enter any other drug's parameters.

Should I use this instead of a formulary?

No. The presets are typical values for orientation and double-checking only. Always confirm doses against a current pediatric formulary such as the BNF for Children, the exact formulation strength, and a second clinician before prescribing.

Is the child's data sent anywhere?

No. All calculations run locally in your browser. Weight and dose values are never transmitted to or stored on a server.

Pediatric Weight-Based Dosing Calculator

Pediatric medicines are dosed by body weight because children vary so widely in size. This calculator multiplies weight by a mg/kg figure, applies a per-dose ceiling so heavier children are not overdosed, and shows both the single and daily doses.

How it works

The core arithmetic is:

per-dose mg  = weight_kg * mg_per_kg_per_dose   (capped at the max per dose)
daily total  = per-dose mg * doses_per_day

Selecting a preset drug loads its typical mg/kg, frequency, and absolute per-dose maximum. If the weight-based figure would exceed that maximum (which happens for larger children), the tool caps the dose and flags it so you can re-check. The custom option lets you enter parameters for any drug.

Example

A 14 kg child given paracetamol at 15 mg/kg per dose receives 14 × 15 = 210 mg per dose, well under the 1000 mg ceiling. At four doses a day that is 840 mg/day, within the 75 mg/kg/day daily limit.

Notes

Presets are orientation values, not a substitute for a current pediatric formulary. Always verify against the exact formulation strength (many pediatric liquids come in several concentrations), the child’s age band, and a second clinician. This is an educational aid that runs entirely in your browser.