Milligrams to Grams (mg to g)

1 milligram equals 0.001 grams exactly.

1 milligram = 0.001 grams

How to convert milligrams to grams

To convert milligrams to grams, multiply the number of milligrams by 0.001. This factor is exact. To go the other way, multiply grams by 1,000.

grams = milligrams × 0.001

Example: 10 milligrams = 0.01 grams.

About these units

Milligram (mg)

Metric (SI)Current unit

One thousandth of a gram. Used for medicine doses and vitamins.

No single inventor can be credited with the milligram. It arrived with the metric system that France introduced in the 1790s, where the gram was the basic unit of mass and thousandths of it were named with a prefix. When the International System of Units was later built around the kilogram, the rule against stacked prefixes meant that a millionth of a kilogram is written 1 mg, never a microkilogram, so the milligram remained a gram-based unit even though the gram itself is not the SI base.

A milligram is small enough that doses of medicine and vitamins are measured in it routinely. A US penny weighs about 2.5 g, so a milligram is roughly one 2,500th of a coin. The unit is also at the center of a well-known safety problem: milligram and microgram differ by a factor of 1,000, and the abbreviation mcg for micrograms is used on prescriptions precisely so that a handwritten micro sign cannot be misread as milli. Confusing the two has caused serious medication errors.

1 milligram = 0.000001 kilograms (exactly).

Sources: Wikipedia: Milligram; Wikipedia: Microgram; Wikipedia: Gram

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

Related conversions

See all weight & mass units.