One milligram is 1,000 micrograms (mcg or µg). Vitamin labels mix the two: vitamin B12 and D are listed in mcg, vitamin C in mg. Always confirm doses with the label or a pharmacist.
How to use the mcg to mg Converter
- Type the number of micrograms into the Micrograms field. Decimals such as 500 are fine.
- Read the answer in Milligrams – it updates as you type, with no button to press.
- To convert the other way, type into Milligrams and the micrograms are recalculated.
- Press Copy results to copy both values with the page title, or Copy link to share this exact conversion.
This page converts only µg ⇄ mg. Need a different unit? Use the general weight converter, where you can choose any “from” and “to” unit.
How it works
Both units measure weight, so they are always in the same ratio: one microgram equals 0.001 milligrams. The calculator multiplies the number of micrograms you type by 0.001 to give milligrams, and when you type into the milligrams field it divides by the same factor to give micrograms. Because the ratio never changes, doubling the micrograms always doubles the milligrams. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation).
How to convert micrograms to milligrams
- Write down the value in micrograms, for example 1,000 µg.
- Multiply by the conversion factor 0.001 (because 1 microgram = 0.001 mg).
- 1,000 × 0.001 = 1 mg.
- To go back from milligrams to micrograms, divide by 0.001 – or multiply by 1,000.
µg to mg conversion table
| Micrograms | Milligrams | Milligrams | Micrograms |
|---|---|---|---|
| 1 µg | 0.001 mg | 1 mg | 1000 µg |
| 10 µg | 0.01 mg | 2 mg | 2,000 µg |
| 25 µg | 0.025 mg | 5 mg | 5,000 µg |
| 50 µg | 0.05 mg | 10 mg | 10,000 µg |
| 100 µg | 0.1 mg | 20 mg | 20,000 µg |
| 250 µg | 0.25 mg | 50 mg | 50,000 µg |
| 400 µg | 0.4 mg | 100 mg | 100,000 µg |
| 500 µg | 0.5 mg | 1,000 mg | 1,000,000 µg |
| 1,000 µg | 1 mg | ||
| 2,500 µg | 2.5 mg | ||
| 5,000 µg | 5 mg |
What is a microgram?
A microgram (µg or mcg) is one millionth of a gram. Potent medicines and some vitamins, such as B12, D and folate, are dosed in micrograms. Doctors often write “mcg” to avoid confusing µ with m.
What is a milligram?
A milligram is one thousandth of a gram. Medicine strengths, vitamins and minerals on supplement labels are usually given in milligrams.
Common mistakes to avoid
Confusing fluid ounces (volume) with ounces (weight), using troy ounces for food or regular ounces for gold, and mixing u.s. short tons, uk long tons and metric tonnes.
Formula
1 µg = 0.001 mg1 mg = 1,000 µgmg = µg × 0.001Worked example
Inputs — Micrograms: 1,000 µg.
Results — Milligrams = 1 mg.
Frequently asked questions
How many mcg in a mg?
1,000.
How many mg is 500 mcg?
0.5 mg.
How many milligrams are in one microgram?
1 µg = 0.001 mg.
How many micrograms are in one milligram?
1 mg = 1,000 µg.
How do I convert micrograms to milligrams?
Multiply the number of micrograms by 0.001. For example, 1,000 µg × 0.001 = 1 mg.
How do I convert milligrams back to micrograms?
Divide by 0.001 (or multiply by 1,000), or simply type the value into the milligrams field above.
What is 10 µg in milligrams?
10 µg = 0.01 mg.
What is 100 µg in milligrams?
100 µg = 0.1 mg.
Is this conversion exact?
Yes. The factor comes from the official definitions of both units (NIST and the SI), so the only difference you may see is rounding in the last displayed digit.
Can I convert to other units on this page?
This page converts only between micrograms and milligrams. To pick any weight unit, use the general weight converter linked under Related calculators.
What formula does the mcg to mg Converter use?
1 µg = 0.001 mg.