Mcg to grams converter, a million micrograms make one gram.

To convert mcg to grams, divide the micrograms by 1,000,000. So 1,000 mcg is 0.001 g, 250 mcg is 0.00025 g and 1,000,000 mcg is exactly 1 g. That is the same as moving the decimal point six places to the left. The conversion is exact. Mcg is the usual label way of writing micrograms, and µg is the same unit. To go the other way, multiply grams by 1,000,000.

How to use the converter

1. Type the amount in the Micrograms (mcg) box. A decimal such as 12.5 works.
2. The big result shows Grams (g). Use Decimals in the side column to fix the number of places.
3. The cards under the result show the same amount in other units.
4. Type in the second box, or press ⇄, to go the other way.
5. Click a row in Common values to load it. Copy result, Copy link, Copy table and Print chart keep the answer. Start again resets the box.
6. Under the tables, Convert a list takes many amounts at once. Paste one per line, for example a column from a spreadsheet, and read them all in the units shown above. Copy results copies the table, and the swap button turns the list around.

Where the million comes from

Micro is the SI prefix for one millionth, 10^-6 (BIPM list of SI prefixes and NIST metric SI prefixes, checked 26 Oct 2026). NIST Handbook 44 (2026), Appendix C lists 1 microgram as 0.000 001 gram exactly. Each step on the prefix ladder is a factor of 1,000, and two steps from mcg to g make 1,000 × 1,000.

Mcg or µg?

Both mean micrograms. US food and supplement labels write mcg: 21 CFR 101.9 (read 26 Oct 2026) lists the unit as "mcg" for micrograms and not µg. Science papers and many other countries write µg. A handwritten µ can be mistaken for an m, which is a thousand times bigger, so mcg is the safer way to write it on a label. When a label shows one unit and a table another, convert, then check that the mcg number is a thousand times the mg number.

Micrograms to grams, in a table

Worked examples

• 1,000 mcg. 1,000 ÷ 1,000,000 = 0.001 g, which is 1 mg.
• 250 mcg. 0.00025 g, or 0.25 mg.
• 50 mcg. 0.00005 g.
• 2,500 mcg. 0.0025 g, or 2.5 mg.
• Grams back to mcg. 0.0004 g × 1,000,000 = 400 mcg.

Mcg is not mg, and it is not IU

The costly slip is a factor of 1,000: 1 mg is 1,000 mcg. A label that lists one item in mg and another in mcg needs care, and this tool will turn either into grams so you can compare them. The unit IU, used for some vitamins, is a different kind of unit. It measures biological activity, and how it relates to mass depends on the substance, so this tool does not turn mcg into IU or the other way.

This page is a unit converter. It changes one unit of mass into another and nothing more. It does not say how much of anything is right for you. For a medicine, a vitamin or a supplement, follow the label and ask a doctor or a pharmacist.

Weighing very small amounts

Remember what 1 mcg is: 0.000001 g. A kitchen scale reads to 1 g or 0.1 g, and a jewelry scale usually reads to 0.01 g or 0.001 g, which is 1,000 mcg. Neither can weigh 50 mcg. The conversion is exact but a physical weighing needs a lab balance, or a stock solution diluted, which this page cannot do.

See also Mg to grams, Grams to mg, Mg to kg and Unit converter.