permilligram

Permilligram is an uncommon, non-SI unit of mass defined as one thousandth of a milligram. By definition, 1 permilligram equals 0.001 milligrams, which is also equal to 1 microgram (µg). The concept arises from combining the per-mille notation (‰) with the milligram, but it does not add practical precision beyond what micrograms already provide.

Usage and note: In contemporary science and industry, the term permilligram is rarely used. When expressing small masses, researchers typically use micrograms or milligrams to maintain clarity and avoid confusion. Because 1 permilligram is identical to 1 microgram, using permilligrams does not change the numerical meaning but can introduce ambiguity in reporting conventions.

Conversions: 1 permilligram = 0.001 mg = 1 µg. Consequently, 5 permilligrams = 0.005 mg = 5 µg, and 1000 permilligrams = 1 mg. If used in concentration or dosage expressions, the same numerical values apply, but the unit remains non-standard and could be misinterpreted.

Relation to standards: Permilligram is not an officially recognized SI unit. For clear communication and consistency, it is generally preferable to express measurements in micrograms or milligrams, depending on the scale, and to avoid non-standard compounded units.

See also: microgram, milligram, parts-per notation.