mg to mL Converter
Convert milligrams (mg) to milliliters (mL) using either the density of a pure substance or the concentration of a solution. For water, 1000 mg = 1 mL.
Frequently Asked Questions
How do you convert mg to mL?
It depends on whether you are dealing with a pure substance or a solution.
Pure substance (using density):
mL = mg ÷ (density × 1,000), where density is in g/mL.
For water: 1,000 mg = 1 mL.
Solution / medication (using concentration):
mL = mg ÷ concentration (mg/mL).
Example: 200 mg of a 5 mg/mL drug = 200 ÷ 5 = 40 mL.
Is 1 mg the same as 1 mL?
No. Milligrams measure mass (how much matter); milliliters measure volume (how much space). They are only numerically equal when the substance density is 1 g/mL and the ratio is expressed as 1,000 mg per 1 mL — which is true for water.
For substances with different densities, you must convert using density or concentration.
How many mL is 100 mg?
For water: 100 mg = 0.1 mL (because 1,000 mg = 1 mL).
For ethanol (density 0.789 g/mL): 100 mg ≈ 0.127 mL.
For a 5 mg/mL medication: 100 mg = 20 mL.
What is the difference between mg and mL?
mg (milligram) is a unit of mass — it tells you how much a substance weighs. 1 gram = 1,000 mg.
mL (milliliter) is a unit of volume — it tells you how much space a substance occupies. 1 liter = 1,000 mL.
Converting between them requires either the density of the pure substance or, for solutions, the concentration (mg per mL).
How do I convert mg to mL for medication?
Read the concentration printed on the bottle — for example "25 mg/mL" — then divide the prescribed dose (in mg) by this number:
mL = dose (mg) ÷ concentration (mg/mL)
Example: a prescription of 150 mg, medication at 25 mg/mL → 150 ÷ 25 = 6 mL.
⚠ Always double-check dosing calculations with a pharmacist or nurse. Do not rely solely on online calculators for medical decisions.
How to Convert mg to mL
There are two common methods depending on what you are converting:
Method 1 — Pure substance (using density)
- Find the density of the substance in g/mL. For water = 1, ethanol = 0.789, olive oil = 0.92, mercury = 13.534.
- Apply the formula: mL = mg ÷ (density × 1,000).
- For water: mL = mg ÷ 1,000. Example: 500 mg = 0.5 mL.
Method 2 — Solution or medication (using concentration)
- Read the concentration from the label (e.g. "5 mg/mL" on a syrup bottle).
- Apply the formula: mL = mg ÷ concentration (mg/mL).
- Example: a 200 mg dose of a 5 mg/mL drug = 200 ÷ 5 = 40 mL.
mg to mL Formula
General formula (pure substances):
For water (density = 1 g/mL):
For solutions with known concentration:
The factor 1,000 comes from converting grams to milligrams (1 g = 1,000 mg) — density is typically expressed in g/mL, so we multiply by 1,000 to match the mg scale.
mg to mL for Water (Quick Reference)
Since water has a density of exactly 1 g/mL, the conversion is simply mL = mg ÷ 1,000. Common values:
| mg | mL |
|---|---|
| 1 mg | 0.001 mL |
| 10 mg | 0.01 mL |
| 100 mg | 0.1 mL |
| 250 mg | 0.25 mL |
| 500 mg | 0.5 mL |
| 1,000 mg | 1 mL |
| 5,000 mg | 5 mL |
| 10,000 mg | 10 mL |
When to Use Density vs Concentration
| Use density when… | Use concentration when… |
|---|---|
| You have a pure substance (water, ethanol, olive oil, mercury). | You have a solution with a label (e.g. "25 mg/mL"). |
| Chemistry lab, material science, cooking ingredient conversion. | Pharmacy, nursing, medication dosing, IV preparation. |
| The "mg" refers to the mass of the substance itself. | The "mg" refers to the amount of active ingredient per mL of solvent. |
Common Substance Densities
Click a row to load that density into the calculator above.
Density values are sourced from the CRC Handbook of Chemistry and Physics and PubChem. Values are reference densities at 20–25 °C unless otherwise noted; real densities vary slightly with temperature and purity. For laboratory work, use the measured density of the actual sample.
| Substance | Density (g/mL) | 1,000 mg = |
|---|---|---|
| Water | 1.000 | 1.000 mL |
| Ethanol | 0.789 | 1.267 mL |
| Olive oil | 0.920 | 1.087 mL |
| Vegetable oil | 0.920 | 1.087 mL |
| Milk (whole) | 1.030 | 0.971 mL |
| Honey | 1.420 | 0.704 mL |
| Glycerol | 1.261 | 0.793 mL |
| Acetone | 0.791 | 1.264 mL |
| Seawater | 1.025 | 0.976 mL |
| Mercury | 13.534 | 0.074 mL |
mg to mL Examples (Water)
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All unit conversions on CoolConversion use conversion factors defined or documented by internationally recognised standards bodies (such as ISO and NIST), including both SI and non-SI units.
