Free converters & iv tool
mg to mcg Converter (and mcg to mg)
To convert mg to mcg, multiply the number of milligrams by 1,000. One milligram equals 1,000 micrograms, so 0.5 mg is 500 mcg and 2.5 mg is 2,500 mcg. To convert mcg to mg, divide by 1,000: 250 mcg is 0.25 mg. This converter does both directions, plus grams, kilograms and nanograms, and shows the math.
Prepared by Prospyr · Reviewed October 3, 2026 · Free, no sign-up, runs in your browser
1 mg equals
1,000mcg
Unit arithmetic only. Dosing decisions belong to the treating provider; check the product label for the concentration and units.
Same amount in every unit
kilograms
0.000001 kg
grams
0.001 g
milligrams
1 mg
micrograms
1,000 mcg
nanograms
1,000,000 ng
mg to mcg conversion table
| mg | mcg |
|---|---|
| 0.1 | 100 |
| 0.25 | 250 |
| 0.5 | 500 |
| 1 | 1,000 |
| 2 | 2,000 |
| 2.5 | 2,500 |
| 5 | 5,000 |
| 10 | 10,000 |
| 25 | 25,000 |
| 50 | 50,000 |
| 100 | 100,000 |
| 250 | 250,000 |
| 500 | 500,000 |
| 1,000 | 1,000,000 |
mg to mcg formula
The metric mass units step by factors of 1,000, which is why the formula is the same every time.
- mg to mcg: mcg = mg × 1,000
- mcg to mg: mg = mcg ÷ 1,000
- g to mg: mg = g × 1,000
- mcg to ng: ng = mcg × 1,000
The SI prefix “milli” means one thousandth and “micro” means one millionth, so a microgram is one thousandth of a milligram. NIST publishes the full prefix list on its metric SI prefixes page.
Worked example: mcg to mg and back
| Start | Math | Result |
|---|---|---|
| 0.25 mg to mcg | 0.25 × 1,000 | 250 mcg |
| 2.5 mg to mcg | 2.5 × 1,000 | 2,500 mcg |
| 500 mcg to mg | 500 ÷ 1,000 | 0.5 mg |
| 75 mcg to mg | 75 ÷ 1,000 | 0.075 mg |
| 1 g to mcg | 1 × 1,000 × 1,000 | 1,000,000 mcg |
Enter any of these in the converter above to check it. Your numbers stay in the page address, so you can send the exact calculation to a colleague.
mcg to mg converter: the same tool in reverse
Press the swap button between the two unit boxes, or tap the “mcg to mg” shortcut under the inputs, and the converter runs mcg to mg. The conversion table below the tool follows whichever pair you have selected, so it doubles as an mcg to mg chart.
If your number is a concentration (mg per mL) rather than an amount, use the mg to mL calculator. For a stock solution you need to dilute, see the dilution calculator.
Keeping units straight in a practice
Unit mix-ups are easy to make, because the same product can be listed in mg on one document and mcg on another. Charting the amount with its unit, in the same place every visit, helps your team catch a mismatch. Prospyr's charting keeps treatment amounts with the rest of the visit record.
Frequently asked questions
How do you convert mg to mcg?
Multiply the milligrams by 1,000. A milligram is one thousandth of a gram and a microgram is one millionth of a gram, so 1 mg = 1,000 mcg. For example, 0.25 mg × 1,000 = 250 mcg.
How do you convert mcg to mg?
Divide the micrograms by 1,000, which moves the decimal point three places to the left. 500 mcg ÷ 1,000 = 0.5 mg, and 50 mcg ÷ 1,000 = 0.05 mg.
Is mcg the same as µg?
Yes. Both mean microgram, one millionth of a gram. The SI symbol is µg (the Greek letter mu), and mcg is the form commonly printed on U.S. product labels and charts.
How many mcg are in a gram?
There are 1,000,000 mcg in 1 gram. A gram is 1,000 mg, and each milligram is 1,000 mcg, so 1,000 × 1,000 = 1,000,000.
How many ng are in an mcg?
There are 1,000 ng in 1 mcg. Each step down the metric ladder from gram to milligram to microgram to nanogram is a factor of 1,000, so 1 mg = 1,000 mcg = 1,000,000 ng.
Does this work for every drug or supplement?
It converts mass units only, so it works for anything measured by weight. It does not convert units of biological activity (IU) or units of any botulinum toxin product, and it does not tell you what amount to give. For IU, use the IU to mcg converter, which only offers NIH-published factors.
Why does a wrong decimal in mg and mcg matter?
A shifted decimal changes the amount by a factor of 10, 100 or 1,000. Writing the unit next to every number, and doing the conversion in one place with the working visible, makes the slip easy to spot. Your protocol's double-check rules still apply.
Sources and scope
- NIST: Metric (SI) Prefixes
Official definitions of the SI prefixes milli, micro and nano, and the rule that mass prefixes attach to the gram.
Unit arithmetic only, not medical advice. It does not recommend an amount, and it does not convert between units of biological activity or between botulinum toxin products. Dosing decisions belong to the treating provider.