Dose Calculator
Calculate medication dose from a prescribed mg/kg amount, body weight, dosing frequency, optional liquid concentration, and optional maximum daily dose.
Results
This calculator only performs dose math from values you enter. It does not recommend medication, dosage, frequency, or treatment. Always use the prescribed dose or product label and confirm medication dosing with a qualified healthcare professional, especially for children, kidney/liver disease, pregnancy, older adults, or high-risk medicines.
Important Note: Medication dosing can be dangerous if units, concentration, body weight, age, kidney/liver function, or prescription instructions are entered incorrectly. Users should always follow the medicine label, prescription, pharmacist, or clinician guidance. NHS states dosage instructions are usually found on the medicine label or patient leaflet, and FDA guidance highlights that unit confusion such as mg versus mL can lead to dosing errors.
Use this Dose Calculator to estimate a medication dose amount based on a prescribed dose, patient weight, medicine strength, and dosing frequency. It can help convert a dose written in milligrams, micrograms, milligrams per kilogram, or liquid concentration into a practical amount such as tablets, mL per dose, or total daily dose.
Important: This calculator is for educational and checking purposes only. It does not prescribe medicine and should not replace instructions from a doctor, pharmacist, prescription label, or patient information leaflet.
Reviewed by: AjaxCalculators Editorial Team
Last updated: May 2026
Method source: Standard dosage, concentration, and weight-based dose formulas
Editorial standards: Built to show transparent formulas, clear assumptions, worked examples, and safety limitations.
What Is a Dose Calculator?
A dose calculator helps estimate how much medicine should be taken per dose when you know the prescribed dose and the medicine strength. It is especially useful when the prescription is written in one unit, such as mg, but the medicine is supplied in another form, such as mg/mL liquid, tablets, capsules, or injections.
For example, if a medicine label says 250 mg per 5 mL and the required dose is 500 mg, the calculator can estimate that the required liquid amount is 10 mL.
What This Calculator Can Estimate
| Calculation Type | What It Means | Example Use |
|---|---|---|
| Fixed dose | A set dose not based on body weight | 500 mg per dose |
| Weight-based dose | Dose calculated from body weight | 10 mg/kg per dose |
| Liquid dose volume | Converts mg dose into mL using concentration | 250 mg/5 mL suspension |
| Tablet or capsule amount | Divides required dose by strength per tablet | 500 mg dose using 250 mg tablets |
| Total daily dose | Multiplies each dose by the number of doses per day | 500 mg three times daily = 1500 mg/day |
Dose Calculator Formulas
1. Fixed Dose Formula
If the prescribed dose is already given as a fixed amount:
Dose per administration = prescribed dose
Example: If the prescription says 500 mg per dose, the dose per administration is 500 mg.
2. Weight-Based Dose Formula
For medicines prescribed by body weight:
Dose = body weight × dose per kg
Example:
- Body weight = 20 kg
- Prescribed dose = 10 mg/kg
- Dose = 20 × 10 = 200 mg
3. Liquid Medicine Formula
For liquid medicines, the calculator converts the required dose into volume:
Volume required = required dose ÷ concentration
If the label says 250 mg per 5 mL, first convert it to mg per mL:
250 ÷ 5 = 50 mg/mL
If the required dose is 500 mg:
500 ÷ 50 = 10 mL
4. Tablet or Capsule Formula
For tablets or capsules:
Number of tablets = required dose ÷ strength per tablet
Example: If the required dose is 500 mg and each tablet is 250 mg:
500 ÷ 250 = 2 tablets
5. Total Daily Dose Formula
To estimate total daily dose:
Total daily dose = dose per administration × number of doses per day
Example: 500 mg taken 3 times daily:
500 × 3 = 1500 mg/day
Worked Example: Liquid Dose Calculation
| Input | Value |
|---|---|
| Required dose | 500 mg |
| Medicine strength | 250 mg per 5 mL |
| Concentration | 50 mg/mL |
| Required volume | 10 mL |
In this example, 250 mg in 5 mL means each 1 mL contains 50 mg. A 500 mg dose therefore requires 10 mL.
Worked Example: Weight-Based Dose
| Input | Value |
|---|---|
| Body weight | 30 kg |
| Prescribed dose | 15 mg/kg |
| Dose per administration | 450 mg |
| Doses per day | 2 |
| Total daily dose | 900 mg/day |
The dose per administration is calculated as 30 × 15 = 450 mg. If taken twice daily, the total daily amount is 900 mg.
How to Use the Dose Calculator
- Enter the patient’s weight if the dose is weight-based.
- Enter the prescribed dose amount.
- Select the correct dose unit, such as mg, mcg, or mg/kg.
- Enter the medicine strength or concentration from the label.
- Enter the dosing frequency if you want the total daily dose.
- Click calculate to view the estimated dose amount.
Understanding the Results
| Result | Meaning |
|---|---|
| Dose per administration | The amount for one dose |
| Liquid volume | The estimated mL amount for one dose |
| Tablet/capsule amount | The calculated number of units needed |
| Total daily dose | The total medicine amount across all doses in 24 hours |
Common Unit Conversions Used in Dosing
| Conversion | Value |
|---|---|
| 1 mg | 1000 mcg |
| 1 g | 1000 mg |
| 1 kg | 2.20462 lb |
| mg/mL | milligrams per millilitre |
| mg/kg | milligrams per kilogram of body weight |
Common Mistakes to Avoid
- Do not confuse mg with mL. Milligrams measure medicine amount, while millilitres measure liquid volume.
- Do not use adult doses for children unless specifically instructed by a qualified clinician.
- Do not guess concentration. Always read the medicine label carefully.
- Do not round tablet or liquid amounts unless a pharmacist or clinician confirms it is safe.
- Do not use this calculator for emergency dosing, chemotherapy, insulin adjustment, anaesthesia, IV infusion titration, or high-risk medicines.
Assumptions and Limitations
- The calculator assumes the entered prescription dose is correct.
- The calculator assumes the medicine strength or concentration is entered exactly as shown on the label.
- It does not check age-specific limits, maximum daily dose, allergies, pregnancy status, kidney function, liver function, or drug interactions.
- It does not decide whether a medicine is appropriate for a condition.
- Results should be verified against the medicine label, prescription, pharmacist, or clinician instructions.
Safety Note for Medication Dosing
Medication dose calculations must be handled carefully. The NHS advises that dosage instructions are usually provided on the medicine packet label or patient information leaflet. FDA medication safety guidance also highlights that confusion between units such as milligrams and millilitres can contribute to medication errors. Always confirm the final dose with a qualified healthcare professional when there is any uncertainty.
Practical Uses
- Checking liquid medicine dose volume from mg and mg/mL concentration
- Estimating weight-based dose amounts
- Calculating total daily dose from dosing frequency
- Understanding tablet or capsule quantity from strength per unit
- Reviewing dose calculations before confirming with a healthcare professional
References
- NHS – Medicines information and dosage instructions
- FDA – Safety considerations to minimize medication errors
- DailyMed – Drug labeling information from the U.S. National Library of Medicine
- MedlinePlus – Reliable medicine and health information from the National Library of Medicine
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Frequently Asked Questions
Can this calculator tell me what medicine dose I should take?
No. This calculator only performs arithmetic based on values you enter. It does not prescribe medicine or decide whether a dose is safe for you.
What is the difference between mg and mL?
mg means milligrams, which measure the amount of medicine. mL means millilitres, which measure liquid volume. Liquid dose calculations require the medicine concentration, such as mg per mL.
How do I calculate a weight-based dose?
Multiply the patient’s weight in kilograms by the prescribed dose per kilogram. For example, 20 kg × 10 mg/kg = 200 mg.
Can I use pounds instead of kilograms?
If the calculator supports pounds, it should convert pounds to kilograms first. Weight-based medication dosing is commonly calculated using kilograms.
Should I round the result?
Only round a medication dose if the medicine label, prescription, pharmacist, or clinician says it is appropriate. Rounding can be unsafe for some medicines.
Is this calculator safe for children’s medicine?
It can help explain the math, but children’s dosing should always be checked against a paediatric prescription, medicine label, or pharmacist guidance.
Can I use this for insulin or IV medicines?
No. Do not use this calculator for insulin adjustment, IV titration, chemotherapy, anaesthesia, emergency medicines, or other high-risk dosing decisions.
Why is medicine concentration important?
Concentration tells you how much active medicine is present in a given volume or unit. Without it, the calculator cannot safely convert a prescribed amount into mL, tablets, or capsules.
Disclaimer: This Dose Calculator is for educational calculation support only. It does not prescribe medicine, confirm whether a medication is suitable, or replace advice from a doctor, pharmacist, prescription label, or patient information leaflet. Medication dosing can be unsafe if the dose, unit, concentration, body weight, age, frequency, kidney/liver function, or medicine form is entered incorrectly. Always verify the final dose with the medicine label or a qualified healthcare professional, especially for children, older adults, pregnancy, chronic conditions, liquid medicines, injections, insulin, IV medicines, or any high-risk medication.