What this calculator does
Converting microgram to milligram is a plain mass-to-mass conversion: a microgram (mcg, sometimes written µg) is one-thousandth of a milligram, and a milligram is one-thousandth of a gram. The relationship between the two is fixed by definition, so converting one to the other is simply a matter of multiplying or dividing by 1,000.
This shows up constantly on supplement labels, medication dosages and nutrition panels, where some ingredients are listed in micrograms (such as vitamin B12 or vitamin D) and others in milligrams, and comparing amounts across labels means putting them on the same scale first.
The formula
To convert micrograms to milligrams, divide by 1,000. To convert milligrams to micrograms, multiply by 1,000. Choose the direction and enter the amount; both figures are shown together for reference.
| Term | Meaning |
|---|---|
| mcg (µg) | Microgram: one-millionth of a gram, or one-thousandth of a milligram. |
| mg | Milligram: one-thousandth of a gram, or 1,000 micrograms. |
| 1,000 | The fixed ratio between the two units, since both are defined as powers of ten of the gram. |
The inputs explained
| Field | What to enter |
|---|---|
| Amount | The amount to convert, in whichever unit you select below. |
| Convert | Choose the unit your amount is currently in, and this converts it to the other one. |
When to use it
Comparing supplement labels
One brand lists a nutrient in micrograms and another in milligrams; converting microgram to milligram (or vice versa) puts both on the same scale so the actual amounts can be compared directly.
Checking a medication dose
A prescription or dosing chart given in one unit can be double-checked against a label or reference given in the other, reducing the chance of misreading a dose by a factor of 1,000.
Converting a nutrition panel figure
Many vitamins and trace minerals are listed in micrograms on nutrition panels; converting to milligrams can make it easier to compare against a personal target or supplement stated in milligrams.
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.
Micrograms converted to milligrams
A range of common microgram amounts and their milligram equivalents.
| Amount (mcg) | In milligrams (mg) |
|---|---|
| 50 | 0.0500 mg |
| 100 | 0.1000 mg |
| 250 | 0.2500 mg |
| 500 | 0.5000 mg |
| 1,000 | 1.000 mg |
| 5,000 | 5.000 mg |
Milligrams converted to micrograms
A range of common milligram amounts and their microgram equivalents.
Questions
How many micrograms are in a milligram?
1,000 micrograms make up 1 milligram. This is a fixed definition of the metric mass units, not an approximation, so the conversion is exact in both directions.
Is this the same as the mg to mL converter on this site?
No. This calculator converts between two mass units, milligrams and micrograms, using a fixed 1,000-to-1 ratio. The mg to mL calculator converts between a mass (milligrams) and a volume (millilitres), which depends on the density of the specific liquid involved and is not a fixed ratio.
Why are some nutrients measured in micrograms rather than milligrams?
Certain vitamins and minerals, such as vitamin B12, vitamin D and folate, are needed in very small daily amounts. Measuring them in micrograms avoids writing awkward, tiny milligram figures like 0.0025 mg, using the smaller unit instead.
Can I trust a straight 1,000-to-1 conversion for medication dosing?
The 1,000-to-1 mass conversion itself is exact and reliable. However, always follow the specific unit given on a prescription or by a pharmacist rather than converting doses yourself for administration, since a misplaced decimal point when converting between mcg and mg is a well-known source of dosing errors.
For blood glucose readings between mg/dL and mmol/L, see the blood sugar converter. For a mass converted against a liquid volume by density, see the mg to mL converter.