Convert Femtometer (fm) to Chain (US Survey) (ch (US)) instantly.
About these units
Femtometer (fm)
A femtometer, equal to 10⁻¹⁵ meters, is the scale at which the structure of atomic nuclei becomes measurable. Also known historically as a "fermi," this unit is used extensively in nuclear physics to describe the radii of protons, neutrons, and nuclei, which typically span 1–10 femtometers. At this scale, the strong nuclear force dominates interactions, and classical intuition breaks down almost entirely—quantum mechanics provides the only meaningful framework. The femtometer also plays a role in high-energy particle experiments, where the wavelengths of probing particles (like high-velocity electrons) may be expressed in femtometer increments. These small wavelengths allow researchers to resolve sub-nuclear structures. While invisible to any optical instrument, distances in the femtometer range can be inferred through scattering experiments, such as those performed in particle accelerators.
Chain (US Survey) (ch (US))
The US Survey Chain is defined as 66 US Survey Feet (~20.1168 meters), aligning with the historic Gunter's chain but adapted to the US survey foot. It is used primarily in cadastral surveys, property delineation, and historical land records. Surveyors employ the chain for practical measurements of fields, lots, and infrastructure layouts. The unit's subdivision into 100 links simplifies area calculation, as 10 square chains equal one acre, maintaining continuity with older surveying systems. Even today, engineers and surveyors working with legacy data encounter the US survey chain in historical deeds, maps, and legal descriptions. Its precision ensures consistency when reconciling pre-modern measurements with modern coordinates.