What this calculator does
mcg to mg is a conversion that matters more than most, because micrograms and milligrams look similar written down but differ by a factor of 1000, and mixing them up on a supplement or medication dose is a real risk rather than just an inconvenience.
This calculator converts mcg to mg by dividing by 1000, or mg to mcg by multiplying by 1000. Enter a value in either unit, choose the direction, and the other comes out immediately, along with the equivalent in grams.
The formula
A milligram is one thousandth of a gram, and a microgram is one thousandth of a milligram, so a microgram is one millionth of a gram. To convert mcg to mg, divide by 1000. To convert mg to mcg, multiply by 1000.
| Term | Meaning |
|---|---|
| Microgram (mcg or µg) | One millionth of a gram, or one thousandth of a milligram. |
| Milligram (mg) | One thousandth of a gram, or one thousand micrograms. |
| 1000x factor | The fixed ratio between the two units: there are always exactly 1000 micrograms in a milligram. |
The inputs explained
| Field | What to enter |
|---|---|
| Value | The value to convert. |
| Convert | Choose whether to convert mcg to mg, or mg to mcg. |
When to use it
Reading a supplement label correctly
Vitamins such as B12 and vitamin D are commonly labelled in micrograms, while a dosage guide or another product might state the same nutrient in milligrams, and mixing the two up understates or overstates the dose by a factor of 1000.
Checking 500mcg to mg
A common supplement dose, such as 500 mcg of a vitamin, converts to 0.5 mg, a figure that is easy to misplace a decimal point on when done by hand.
Converting a medication dose between the units it is prescribed and labelled in
Some medications are prescribed in one unit and packaged in another; converting confirms the dose on the label matches the dose intended, though any dosing decision should still be checked against the actual prescription or packaging.
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.
mcg to mg, at common supplement dose values
A range of microgram values, each converted to milligrams.
| Micrograms | Milligrams | In grams |
|---|---|---|
| 50 | 0.050000 | 0.00005000 g |
| 100 | 0.100000 | 0.000100 g |
| 250 | 0.250000 | 0.000250 g |
| 500 | 0.500000 | 0.000500 g |
| 1000 | 1.0000 | 0.001000 g |
| 2000 | 2.0000 | 0.002000 g |
mg to mcg, at common values
A range of milligram values, each converted to micrograms.
| Milligrams | Micrograms | In grams |
|---|---|---|
| 0.1 | 100.000 | 0.000100 g |
| 0.5 | 500.000 | 0.000500 g |
| 1 | 1,000.00 | 0.001000 g |
| 5 | 5,000.00 | 0.005000 g |
| 10 | 10,000.00 | 0.010000 g |
| 100 | 100,000.00 | 0.100000 g |
Questions
How many mcg in a mg?
Exactly 1000 micrograms in a milligram. To convert mg to mcg, multiply by 1000; to convert mcg to mg, divide by 1000.
What is 500mcg to mg?
500 mcg ÷ 1000 = 0.5 mg.
Is mcg the same as µg?
Yes, mcg and µg both stand for microgram, one millionth of a gram. "mcg" is used on many labels because the µ (mu) symbol does not display reliably on all printers and screens.
Why do supplement labels sometimes use mcg and sometimes mg for the same nutrient?
The unit chosen usually depends on the typical dose size: nutrients needed in very small amounts, such as vitamin B12 or vitamin D, are labelled in micrograms so the number is not an awkward small decimal, while nutrients needed in larger amounts use milligrams.
For a wider mass and weight ladder, milligrams up to tonnes, see the weight and mass converter. For converting a vitamin dose between micrograms and international units, see the vitamin mcg to IU converter.