Grams to Micrograms (g to µg)

1 gram equals 1,000,000 micrograms exactly.

1 gram = 1,000,000 micrograms

How to convert grams to micrograms

To convert grams to micrograms, multiply the number of grams by 1,000,000. This factor is exact. To go the other way, multiply micrograms by 0.000001.

micrograms = grams × 1,000,000

Example: 10 grams = 10,000,000 micrograms.

About these units

Gram (g)

Metric (SI)Current unit

One thousandth of a kilogram. The standard unit for food quantities and small objects.

A gram was once defined as a small drop of the natural world. The French National Convention of 1795 set it as the absolute weight of a volume of pure water equal to a cube one hundredth of a metre on each side, a cubic centimetre. The reference temperature was first the melting point of ice and was later changed to the temperature of maximum density of water, about 4 degrees Celsius. The word came into French as gramme, from Late Latin gramma, itself from the Greek for a letter or small mark; in Late Antiquity it meant about one twenty-fourth of an ounce.

The gram was the base unit of mass in the centimetre-gram-second system, but in 1960 the SI took the kilogram as its base unit, which made the gram one thousandth of it. That is why it appears in so many everyday places: it is the standard for non-liquid ingredients in cooking and shopping, and nutrition labels commonly list contents per 100 g. For a sense of scale, a small paper clip or a pen cap weighs about a gram, and a Japanese 1-yen coin is close to exactly that, while a US penny is around 2.5 g.

1 gram = 0.001 kilograms (exactly).

Sources: Wikipedia: Gram; Wikipedia: Kilogram

Microgram (µg)

Metric (SI)Current unit

One millionth of a gram. Used for very small doses such as vitamin B12 and folic acid; often written mcg on labels.

Tiny doses forced the microgram into everyday use. It is one millionth of a gram, written with the SI prefix micro and the Greek letter mu, but that letter caused trouble: handwritten or badly printed, mu can look like a lowercase m, which would turn micro into milli and make a dose a thousand times too large. For that reason the US Institute for Safe Medication Practices and the FDA recommend writing mcg in medical communication, while UK prescribing guidance says microgram should be written out in full rather than abbreviated.

You meet the unit mostly on nutrition labels and in medicine, where amounts such as folic acid and vitamin B12 are given in micrograms. It also matters in laboratories. According to NIST, the old kilogram prototype gave relative uncertainties of a few parts in ten thousand at the milligram level, and fields such as pharmaceuticals and materials science increasingly need dependable accuracy down at the microgram, which was one argument for redefining the kilogram with a fundamental constant. In text where mu is unavailable, people type u or the micro sign instead.

1 microgram = 1×10⁻⁹ kilograms (exactly).

Sources: Wikipedia: Microgram; NIST: Kilogram introduction (SI redefinition)

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