Mg to Mcg Converter

A milligram (mg) is one thousandth of a gram. A microgram (mcg) is one millionth of a gram. That makes 1 mg equal to 1,000 mcg, so going from mg to mcg means moving the decimal point three places to the right¹.

What Mg to Mcg Conversion Measures

This tool changes the unit, not the amount. 0.9 mg and 900 mcg are the same quantity written two ways. It does not tell you how much of a nutrient anyone needs, and it does not compare your number with a recommended intake.

The Formula

Metric prefixes are powers of ten. Milli means 10⁻³ and micro means 10⁻⁶, so the ratio between them is exactly 1,000 by definition¹.

Micrograms = milligrams x 1,000

Milligrams = micrograms / 1,000

How This Calculator Computes Your Result

Type the number printed on the label, in mg. Decimals are allowed, for example 1.7. The tool multiplies by 1,000 by shifting the decimal point, so the answer is exact and is never rounded. Results appear in plain decimal form with a leading zero, so 0.0005 mg shows as 0.5 mcg. Trailing zeros are dropped, so 1.0 mg shows as 1 mg. The swap button opens the Mcg to Mg Converter with your result filled in, and the copy button copies the number.

What Your Result Means

The mcg number is always 1,000 times bigger than the mg number. This table converts some of the Daily Values that US labels list in mg, for adults and children aged 4 and older².

A quick sanity check: an amount from 1 mg to just under 10 mg should land in the thousands of mcg, and an amount from 0.1 mg to just under 1 mg should land in the hundreds. If 1.7 mg gives 17 or 170,000, the decimal moved the wrong number of places.

Mg to Mcg Conversion Table

Comparing a Label With an RDA or UL

Labels list many minerals and B vitamins in mg. Some reference figures use mcg instead. The NIH copper fact sheet gives its RDA and upper limit in mcg, while the label Daily Value is 0.9 mg³. Convert one side first, then compare.

The RDA is the average daily intake level sufficient to meet the needs of nearly all healthy people. The UL is the maximum daily intake unlikely to cause adverse health effects³. Here are the adult figures from three NIH fact sheets, shown in both units.

Sources for the rows: copper³, zinc⁴, vitamin B6⁵. Supplement amounts show why the unit matters. The copper fact sheet says supplements typically range from a few micrograms to 15 mg³. Fifteen mg is 15,000 mcg, which is about 17 times the Daily Value. The same fact sheet notes that its ULs do not apply to people taking copper under medical supervision³.

Decimal Points and Trailing Zeros

Unit mix-ups are not the only risk. The Institute for Safe Medication Practices (ISMP) lists "µg" as an error-prone abbreviation because it can be mistaken for mg, and advises "mcg"⁶. Swapping mg and mcg is a 1,000-fold error.

ISMP also flags two decimal point slips. A trailing zero (1.0 mg) can be mistaken for 10 mg if the decimal point is not seen. A missing leading zero (.5 mg) can be mistaken for 5 mg⁶. This converter always shows a leading zero and drops trailing zeros, so 0.5 mg gives 500 mcg and 1.0 mg gives 1,000 mcg.