Micrograms to milligrams:
divide by 1,000

How many milligrams are in a microgram?

One microgram is 0.001 milligrams. Put the other way, 1,000 micrograms equal exactly 1 milligram. Both units are metric: a milligram is a thousandth of a gram and a microgram is a thousandth of a milligram, so the step between them is a clean factor of 1,000.

You will see micrograms written as µg or, more often on labels, as mcg. They mean the same thing. Many labels use mcg because the Greek letter mu can be misread or lost in printing.

The mcg to mg formula

Because dividing by 1,000 only moves the decimal point three places, you rarely need a calculator for round numbers. 250 mcg is 0.25 mg, and 50 mcg is 0.05 mg.

1. 1Write the amount in micrograms.
2. 2Move the decimal point three places to the left, or divide by 1000.
3. 3Check the unit on the answer: it should now read mg.
4. 4Confirm the result is smaller than the starting number.

Chart: micrograms to milligrams

This table covers the values most often seen on labels and test results.

Every row is the micrograms figure divided by 1,000, so you can extend the table: 2000 mcg is 2 mg and 5000 mcg is 5 mg.

Where mcg to mg conversions turn up

Supplement labels are the everyday case. A vitamin D tablet might list 25 mcg while a magnesium tablet lists 200 mg, and comparing them means putting both in the same unit: 25 mcg is only 0.025 mg. Lab reports, trace elements in food and some skin-care ingredient lists work the same way.

A second worked example: a multivitamin lists vitamin B12 at 2.4 mcg and a separate lozenge lists 0.5 mg. Converting the lozenge, 0.5 mg is 500 mcg, which is far more than 2.4 mcg. Putting both in micrograms makes that obvious at a glance.

Reading labels is easier if you decide on one unit before you compare products. Convert everything to micrograms when most of the figures are small, or to milligrams when most are large. Mixed lists, where one nutrient reads 0.05 mg and another reads 50 mcg, hide the fact that these are identical amounts.

A sanity check that works every time: the milligram number should have exactly three fewer digits before the decimal point than the microgram number once you account for zeros. 1,000 has four digits and becomes 1, while 25 becomes 0.025. If your answer does not follow that pattern, recheck the decimal.

Common mistakes when converting mcg to mg

• Moving the decimal the wrong way. Going from mcg to mg makes the number smaller, so 400 mcg becomes 0.4 mg, not 400,000 mg.
• Moving it the wrong distance. The step is three places, not two or six. Micrograms to grams would be six places.
• Confusing mcg with mg on a label. They differ by a factor of 1,000, so always read the unit as well as the number.
• Mixing up the symbols. The prefix mu (µ) means micro, while a capital M would mean mega, which is not used for mass on labels.