fg

Fg commonly refers to the femtogram, a unit of mass in the metric system. The femtogram equals 10^-15 grams, or 10^-18 kilograms. It is formed by the prefix femto (10^-15) and the gram. While not a base SI unit, the femtogram is an accepted subunit used for extremely small masses in fields such as biochemistry, nanotechnology, and molecular physics.

Because it measures masses on a very small scale, quantities expressed in femtograms appear in studies of biomolecules, nanoparticles, and trace analyses. For perspective, a single base pair of DNA has a mass of about 1.1 × 10^-21 grams, roughly 10^-6 femtograms, illustrating how tiny fg-scale masses are. In practice, researchers may report masses in fg, picograms (10^-12 g), or higher scales depending on context.

Measuring femtogram masses requires specialized instrumentation, including high-sensitivity microbalances, resonant mass sensors, and advanced mass spectrometry or optical methods. These tools enable detection and quantification of minute masses in research and development.

Note: The standard symbol for the unit is 'fg' (lowercase f). 'Fg' is not the conventional notation and may cause confusion.

See also: Attogram, picogram, nanogram, microgram; kilogram; mass spectrometry.