What this calculator does
Mg to ml is not a straightforward conversion, because milligrams measure mass and millilitres measure volume, and the two only line up directly for water, where 1 mL happens to weigh almost exactly 1000 mg. Any other liquid, from a medicine syrup to an oil-based liquid, weighs a different amount for the same volume.
This calculator converts mg to ml or ml to mg for water and several other common liquids, or for a custom density entered directly, using the relationship that mass equals volume multiplied by density. It is built for everyday dosing and kitchen conversions, not as medical advice; always follow a label or a pharmacist for anything taken as medicine.
The formula
Density links the two units: mass (mg) equals volume (mL) multiplied by density (mg/mL). Dividing mg by density gives mL; multiplying mL by density gives mg. Water is the one liquid where this is a straight 1:1 swap, because 1 g/mL is defined as its density at typical conditions, which is 1000 mg per mL.
| Term | Meaning |
|---|---|
| Density | Mass per unit volume. Here it is shown in g/mL for readability and used internally as mg/mL, since 1 g/mL equals 1000 mg/mL. |
| mg to ml | Volume = mass ÷ density. For water this is dividing by 1000; for a denser liquid like a syrup, the resulting volume is smaller for the same mass. |
| ml to mg | Mass = volume × density: the reverse direction, useful when a dose or recipe is specified by volume but needs converting to a weight. |
The inputs explained
| Field | What to enter |
|---|---|
| Amount | The amount to convert, either a mass in milligrams or a volume in millilitres, depending on the direction chosen below. |
| Convert | Whether you are converting milligrams to millilitres, or millilitres to milligrams. |
| Liquid / density | The liquid being measured, or "Custom density" to enter a specific density instead of picking from the list. |
| Custom density (g/mL) | Only used when "Custom density" is selected above: the density of the liquid, in grams per millilitre. |
When to use it
Converting a liquid medicine dose given by weight
A dose specified as a certain number of milligrams of active ingredient converts to a volume in millilitres when the liquid is measured with a dosing syringe or spoon, using the density of that particular preparation.
Checking a small-volume dose in mg for consistency
Working from a millilitre measurement back to milligrams checks that a labelled dose and a measured volume agree, useful when comparing two ways the same amount is described.
Converting a kitchen or lab quantity that only makes sense in mg
Very small liquid amounts, such as flavouring drops or a lab reagent, are sometimes specified in milligrams; converting to millilitres gives a volume that is easier to measure with a dropper or micropipette.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many mL is 500 mg, across common liquids?
The same 500 mg mass, converted to a volume for each liquid in the list.
| Liquid | Millilitres | Density used |
|---|---|---|
| Water | 0.5000 mL | 1.000 g/mL (1,000 mg/mL), Water |
| Saline solution | 0.4975 mL | 1.005 g/mL (1,005 mg/mL), Saline solution |
| Medicine syrup | 0.3846 mL | 1.300 g/mL (1,300 mg/mL), Medicine syrup |
| Ethanol | 0.6337 mL | 0.789 g/mL (789 mg/mL), Ethanol |
| Glycerin | 0.3968 mL | 1.260 g/mL (1,260 mg/mL), Glycerin |
| Oil-based liquid | 0.5435 mL | 0.920 g/mL (920 mg/mL), Oil-based liquid |
mg to mL for water, at common dose amounts
A range of milligram amounts of water, each converted to millilitres.
| Milligrams | Millilitres | In grams |
|---|---|---|
| 100 | 0.1000 mL | 0.1000 g |
| 250 | 0.2500 mL | 0.2500 g |
| 500 | 0.5000 mL | 0.5000 g |
| 1000 | 1.000 mL | 1.000 g |
| 5000 | 5.000 mL | 5.000 g |
Questions
How do I convert mg to ml?
Divide the mass in milligrams by the liquid's density in mg/mL. For water, divide by 1000; for a denser liquid such as a syrup, dividing by its higher density gives a smaller volume for the same mass.
Is 1 mg the same as 1 ml?
No, and only for water are the two even close on a 1:1000 basis (1000 mg = 1 mL). Milligrams measure mass and millilitres measure volume; they are only convertible once a density is known.
What is a dose calculator mg/ml used for?
A dose given as a concentration in mg/mL, such as a liquid medicine strength, is used to work out how many millilitres deliver a target milligram dose, by dividing the target dose by the concentration.
How is mg to ml drug conversion different from a plain unit conversion?
A drug's mg to ml conversion depends on its specific formulation strength (for example, "50 mg/mL"), set by the manufacturer, not on the physical density of the liquid alone, so the correct figure always comes from the product label rather than a general calculator.
For grams and millilitres of kitchen liquids like milk or honey, see the grams to mL converter. To convert a density value itself between units, see the density unit converter.