Health reference

Medication Dosage by Weight

A transparent mg/kg calculator for learning and double-checking arithmetic. It converts weight, applies per-dose or per-day dosing, respects maximum doses and converts the result to a liquid volume, showing each step.

For education and checking arithmetic only. Do not use it to decide a dose. Always follow a clinician's instructions or the product label.
-Enter weight and dose.
-Weight in kg
-Total per day
-Dosing interval
-Effective dose per kg

    Working

      Educational reference only - always confirm doses with a doctor, pharmacist or the product label. Runs entirely in your browser.

      Why show the working

      Catch slips

      Unit mix-ups between lb and kg or mg and mcg are a classic source of dosing errors.

      Learn the method

      Each step mirrors the method taught in nursing and pharmacy dosage calculations.

      Respect maximums

      Caps for single and daily doses are applied and flagged automatically.

      How to use the calculator

      1. Enter weight and doseType the body weight and the prescribed dose per kilogram, and choose per dose or per day.
      2. Add limits and frequencyPick doses per day and enter any maximum single or daily dose.
      3. Convert to volumeEnter the liquid concentration to see the mL to measure, then review each step.

      How weight-based dosing works

      Many medicines, especially for children, are prescribed per kilogram of body weight. The dose equals weight in kilograms multiplied by the mg/kg amount. Pounds must be converted first: 1 lb = 0.4536 kg.

      Doses are then checked against maximums. A heavy teenager may calculate to more than an adult dose, so the adult maximum applies. Finally, liquids are measured by volume, which depends on the product concentration.

      Convert weight

      kg = lb x 0.4536.

      Calculate dose

      mg = kg x mg/kg.

      Convert to volume

      mL = mg / (mg per mL).

      Dosage by weight FAQ

      Is this calculator a substitute for medical advice?

      No. It is for education and for double-checking arithmetic only. Always follow the dose on the product label or from a doctor or pharmacist, and never exceed the stated maximum.

      What is the difference between per dose and per day?

      A per-dose order such as 10 mg/kg/dose is given each time. A per-day order such as 30 mg/kg/day is the total for 24 hours, divided into the number of doses.

      How is the liquid volume worked out?

      Volume (mL) = dose (mg) / concentration (mg per mL). For example 160 mg in 5 mL is 32 mg/mL, so a 240 mg dose is 7.5 mL.

      Why does the result say capped?

      Weight-based doses can exceed the adult maximum in heavier people. When the calculated dose is above the maximum single or daily dose you enter, the tool uses the maximum instead and tells you.

      Should I round the volume up or down?

      Rounding to the nearest syringe mark is common. The exact unrounded volume is always shown so a professional can decide.

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