mL to mg Converter
Convert milliliters (mL) to milligrams (mg) using either the density of a pure substance or the concentration of a solution. For water, 1 mL = 1,000 mg.
Frequently Asked Questions
How do you convert mL to mg?
It depends on whether you are dealing with a pure substance or a solution.
Pure substance (using density):
mg = mL × density × 1,000, where density is in g/mL.
For water: 1 mL = 1,000 mg.
Solution / medication (using concentration):
mg = mL × concentration (mg/mL).
Example: 10 mL of a 5 mg/mL drug = 10 × 5 = 50 mg of active ingredient.
Is 1 mL the same as 1 mg?
No. Milliliters measure volume; milligrams measure mass. For water, 1 mL = 1,000 mg (not 1 mg), because 1 mL of water weighs 1 gram and 1 gram = 1,000 mg.
For substances with different densities, the conversion differs.
How many mg is 1 mL?
For water: 1 mL = 1,000 mg.
For ethanol (density 0.789 g/mL): 1 mL ≈ 789 mg.
For a 5 mg/mL medication: 1 mL = 5 mg of active ingredient (the rest is solvent).
What is the difference between mL and mg?
mL (milliliter) is a unit of volume — how much space a substance occupies. 1 liter = 1,000 mL.
mg (milligram) is a unit of mass — how much a substance weighs. 1 gram = 1,000 mg.
Converting between them requires either the density of the pure substance or, for solutions, the concentration (mg per mL).
How do I convert mL to mg for medication?
Read the concentration printed on the bottle — for example "25 mg/mL" — then multiply the volume (in mL) by this number:
mg = volume (mL) × concentration (mg/mL)
Example: you administered 6 mL of a 25 mg/mL medication → 6 × 25 = 150 mg of active ingredient.
⚠ Always double-check dosing calculations with a pharmacist or nurse. Do not rely solely on online calculators for medical decisions.
How to Convert mL to mg
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: mg = mL × density × 1,000.
- For water: mg = mL × 1,000. Example: 0.5 mL = 500 mg.
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: mg = mL × concentration (mg/mL).
- Example: 40 mL of a 5 mg/mL drug = 40 × 5 = 200 mg.
mL to mg 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.
mL to mg for Water (Quick Reference)
Since water has a density of exactly 1 g/mL, the conversion is simply mg = mL × 1,000. Common values:
| mL | mg |
|---|---|
| 0.01 mL | 10 mg |
| 0.1 mL | 100 mg |
| 0.25 mL | 250 mg |
| 0.5 mL | 500 mg |
| 1 mL | 1,000 mg |
| 5 mL | 5,000 mg |
| 10 mL | 10,000 mg |
| 100 mL | 100,000 mg |
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" you get is the total mass of the substance. | The "mg" you get is the amount of active ingredient in that volume. |
Common Substance Densities
Click a row to load that density into the calculator above.
| Substance | Density (g/mL) | 1 mL = |
|---|---|---|
| Water | 1.000 | 1,000 mg |
| Ethanol | 0.789 | 789 mg |
| Olive oil | 0.920 | 920 mg |
| Vegetable oil | 0.870 | 870 mg |
| Milk (whole) | 1.049 | 1,049 mg |
| Honey | 1.360 | 1,360 mg |
| Glycerol | 1.261 | 1,261 mg |
| Acetone | 0.791 | 791 mg |
| Seawater | 1.025 | 1,025 mg |
| Mercury | 13.534 | 13,534 mg |
mL to mg 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.
