mg to mL Calculator
Written & clinically reviewed by George Lambroglou, RN • Updated 23 Dec 2025
Convert a dose in milligrams (mg) to a measurable volume in millilitres (mL) using the medication concentration (mg/mL).
Important: This page is a medication dose-to-volume calculator (uses mg/mL from the product label). Some “mg to mL” tools online convert using density (e.g., water/oil/ingredients). For medication administration, use the labeled concentration (mg/mL or mg per X mL).
Enter the dose in milligrams. Commas accepted (e.g., 10,000).
Concentration in mg per mL. Leave blank if using the label helper below.
How mg to mL Conversion Works
A medication order is often written as a dose in milligrams (mg), but you administer a volume (mL). The bridge between those is the concentration on the label: mg per mL (mg/mL).
If you know the concentration, the conversion is straightforward: divide the dose (mg) by how many mg are in each mL (mg/mL). That gives you the volume to draw up or prepare.
Many labels aren’t written as mg/mL — they’re written as mg per X mL (e.g., 250 mg/5 mL). You can convert that label format into mg/mL by dividing the label mg by the label mL, then use the standard formula.
Quick checklist: Confirm (1) ordered dose (mg), (2) product concentration (mg/mL or mg per X mL), (3) you’re using the right product/strength, and (4) your result is measurable with your device (syringe/bag per local policy).
Formula
If the label is in mg per X mL, convert first: mg/mL = mg ÷ mL.
Worked Examples
Example 1: A patient is prescribed 500 mg. The solution is 50 mg/mL. How many mL do you give?
mL = 500 ÷ 50
Example 2: The label reads 250 mg in 5 mL. The dose is 125 mg. How many mL is the dose?
Step 2: mL = 125 ÷ 50 = 2.5
Example 3: Dose is 125 mg. Concentration is 40 mg/mL. What is the volume to 2 decimals?
Practice Questions (with Answers)
Use these to check your understanding. Click Show answer to reveal the working out.
Practice 1: Order is 500 mg. Stock concentration is 50 mg/mL. How many mL will you administer?
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Practice 2: Label reads 250 mg/5 mL. Order is 125 mg. How many mL is the dose?
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Practice 3: Order is 2 mg. Stock is 50 mg/mL. What mL does the calculator produce (before rounding)?
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Practice 4: Order is 125 mg. Stock is 40 mg/mL. What is the volume (to 2 decimals)?
Show answer
When This Calculator Is Used
- •Converting a prescribed dose (mg) into a measurable volume (mL)
- •Converting “mg per X mL” labels (e.g., 250 mg/5 mL) into mg/mL
- •Double-checking arithmetic during medication prep and documentation
- •Study and exam practice for nursing, pharmacy, and junior medical staff
Clinical reminder: Always confirm the ordered dose, product concentration, and local policies. This calculator supports calculation checking but does not replace clinical judgement.
Related Calculators
Frequently Asked Questions
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & Study Sources
These references support the core dose calculation method and medication math practice used on this page.
OpenStax – Pharmacology for Nurses (Dosage Calculations)
Drug calculation methods and unit consistency (open textbook).
University of South Australia – Dosage Calculation Worksheet (PDF)
Worked practice approach to medication dosage calculations (worksheet).
University of South Australia – Worksheet Answers (PDF)
Answer key with worked solutions (supports verification).
York St John University – Nursing Formula Sheet (PDF)
Quick guide formulas for dosage calculations.
Flinders University – Drug Calculations (PDF)
Academic numeracy guide covering core medication maths.
Clinical Disclaimer: Always verify vial labels, prescriptions, and local policy. Educational use only.