# Dosage Calculator (mg/kg)

URL: https://speedycalculator.com/calculators/health/dosage/
Last updated: 2026-10-30

> The dosage calculator works out a weight-based dose from a prescribed amount in mg per kg, the dose per administration, the daily total and – for liquid medicines – the volume to give from the concentration on the label. Always follow your prescriber's instructions.

## Inputs

- Weight (kg, lb, st, g)
- Prescribed dose (mg/kg per dose)
- Doses per day
- Liquid concentration (mg/mL)
- Maximum single dose (0 = none) (mg)

## Results

- Dose per administration
- Volume per dose
- Total per day
- Interval between doses

## Formula

```
Dose per administration = weight (kg) × dose (mg/kg)
Volume (mL) = dose (mg) ÷ concentration (mg/mL)
Daily total = dose × doses per day (check against the maximum daily dose)
```

## Explanation

Many medicines, especially for children, are prescribed per kilogram of body weight. Dosing errors – such as confusing mg and mL or misplacing a decimal point – are a common cause of harm, so every calculation should be double-checked against the label or by a pharmacist.

### How to use the Dosage Calculator

- **Weight**
- **Prescribed dose**
- **Doses per day**
- **Liquid concentration**
- **Maximum single dose (0 = none)**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the weight, the prescribed mg/kg dose, the number of doses per day and the liquid concentration. Enter a maximum single dose to cap the result if your prescriber gave one.

### Inputs explained

FieldWhat to enterWeightUnits: kg, lb, st, gPrescribed doseIn mg/kg per doseDoses per dayA numberLiquid concentrationIn mg/mLMaximum single dose (0 = none)In mg

### What each result means

- **Volume per dose** = [Dose per administration]÷[Liquid concentration]
- **Total per day** = [Dose per administration]×[Doses per day]
- **Interval between doses** = 24÷[Doses per day]

### Example values

How the main result changes when **Weight** changes and everything else stays at the example values above:

Weight (kg)Dose per administration (mg)101001515020200252503030040400
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Weight: 20 kg; Prescribed dose: 10 mg/kg per dose; Doses per day: 3; Liquid concentration: 40 mg/mL; Maximum single dose (0 = none): 0 mg.

Results — **Dose per administration = 200 mg**; Volume per dose = 5 mL; Total per day = 600 mg; Interval between doses = 8 hours.

## Key terms

- **mg/kg**: Milligrams of medicine per kilogram of body weight.

## FAQ

**How do I measure a liquid dose accurately?**
Use an oral syringe or the measuring device supplied – never a kitchen spoon.

**What if the calculated dose exceeds the adult dose?**
Never exceed the maximum stated on the label or by the prescriber.

**Should I use actual or ideal weight?**
Follow the medicine's guidance – some use ideal or adjusted weight in obesity.


## Sources

- [Institute for Safe Medication Practices – Preventing dosing errors](https://www.ismp.org/)