Convert Kilogram (kg) to Femtogram (fg) instantly.
About these units
Kilogram (kg)
The kilogram is the base unit of mass in the SI system and the only SI unit defined directly by a fundamental constant rather than a physical object. Originally, its definition was tied to a platinum–iridium artifact stored in France—the famous "International Prototype Kilogram." Over time, tiny mass changes in the prototype and its official copies created difficulties for high-precision science. In 2019, the kilogram was redefined using Planck's constant, linking mass to the laws of quantum physics through the Kibble balance. This innovation ensures universality, stability, and reproducibility across the world. The kilogram is central to commerce, science, engineering, and every quantitative field dealing with matter. Its decimal relationships with other metric units (grams, milligrams, tons) make it universally convenient. From groceries to spacecraft mass budgets, the kilogram anchors modern mass measurement.
Femtogram (fg)
A femtogram is 10⁻¹⁵ grams, an extraordinarily small unit used primarily in molecular biology, analytical chemistry, and particle science. At this scale, masses correspond to small clusters of molecules, fragments of genetic material, or trace contaminants in environmental samples. In genomics, for example, the femtogram level may represent the mass of DNA extracted from just a few cells, pushing the limits of current sequencing technologies. Advanced mass spectrometers and nanoscale resonators can detect femtogram-level differences, revealing chemical changes invisible at larger scales. The femtogram symbolizes the reach of modern science into realms once thought beyond measurement. As techniques continue to improve, femtogram-level precision will become increasingly common in nanotechnology and biophysics.