Understanding mg vs. mcg

A milligram (mg) is one thousandth of a gram. A microgram (mcg or µg) is one thousandth of a milligram. So 1 mg = 1,000 mcg, and 0.25 mg = 250 mcg.

Vials are usually labelled in milligrams while research amounts are often expressed in micrograms, which is exactly the conversion where thousand-fold errors occur.

A habit that prevents it

Convert everything to one unit before calculating, and write the unit next to every number. Our calculator does both and labels every result explicitly.