Calculator — dose by weight

mg/kg dose calculator

Work out a dose from mg/kg and weight, then the volume to give.

Short answer: Dose (mg) = mg/kg × weight (kg). Then volume (ml) = dose ÷ strength (mg/ml). 15 mg/kg for a 12 kg child is 180 mg, which is 3.6 ml of a 250 mg in 5 ml liquid.

mg/kg dose calculator

Enter the prescribed mg/kg, the weight and, optionally, the strength.

Calculate a dose by weight

Dose (mg/kg)

Weight (kg)

Strength (mg)

in volume (ml)

Dose (mg) = mg/kg × weight (kg)

Volume (ml) = Dose ÷ Strength × Volume of strength

Example: 15 mg/kg, 12 kg. 15 × 12 = 180 mg. The liquid is 250 mg in 5 ml, so 180 ÷ 250 × 5 = 3.6 ml.

See also dose per kg and body surface area and the daily dose calculator. Calculators are for practice and checking. In practice always follow your organisation's policy.

Frequently asked questions

How do you calculate a dose per kg?+

Multiply the prescribed mg/kg by the patient's weight in kg.

How do I turn mg into ml?+

Divide the dose by the strength and multiply by the volume the strength is in. 180 mg of a liquid with 250 mg in 5 ml is 3.6 ml.

Is this for clinical use?+

No. It is for practice and checking only. Follow your organisation's policy in practice.

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Practise weight-based doses

Dos is a practice app for drug calculations. It has practice tests of ten questions, a built-in calculator next to each question, and statistics per topic.

Practice questions