Femtogram

Femtogram (fg) is a unit of mass in the metric system. It denotes one quadrillionth of a gram (10^-15 g) or 10^-18 kilograms.

In scientific contexts such as chemistry, molecular biology, and nanotechnology, femtograms describe masses of very small biological macromolecules and nanoscale materials. One femtogram is about 6×10^8 unified atomic mass units (Daltons), roughly 600 megaDaltons, which corresponds to the mass of large protein complexes or small virus particles.

Measuring masses at the femtogram scale requires specialized instrumentation. Common methods include highly sensitive microbalances, mass spectrometry with extreme precision, and nano-scale cantilever sensors.

Related units and conversions: 1 fg equals 1000 attograms (ag) and 0.001 picograms (pg). In terms of atomic mass units, 1 fg is approximately 6.0×10^8 Da. This scale sits between attograms and picograms in the metric hierarchy and is routinely used in fields dealing with extremely small masses.