Convert Span (Cloth) (span) to Parsec (pc) instantly.
About these units
Span (Cloth) (span)
The span is a unit traditionally used in textile measurement, equal to the distance between the tip of the thumb and the tip of the little finger when the hand is fully extended, approximately 22.86 cm (9 inches). This anthropometric unit was widely used by weavers and cloth merchants to measure lengths of fabric quickly and intuitively. Its small scale made it convenient for practical applications where tape measures or rulers were unavailable. The span also appears in cultural and historical texts as a natural unit of human proportion. While largely obsolete today, it offers insight into pre-industrial textile practices and the anthropometric basis of early measurement systems.
Parsec (pc)
A parsec is equal to 3.26 light years, or approximately 3.0857 × 10¹⁶ meters. It is defined based on the method of stellar parallax, the apparent shift in a star's position caused by Earth's orbit around the Sun. Specifically, a star at a distance of one parsec exhibits a parallax angle of one arcsecond (1/3600 of a degree). Because its definition emerges directly from geometric measurement techniques, the parsec became the standard astronomical unit for professional research. Parallax-based distances are foundational to the cosmic distance ladder — the sequence of methods by which astronomers measure distances from nearby stars to the farthest galaxies. The parsec is widely used in astrophysics because calculations involving gravitational dynamics, luminosity, or galactic structure often become more intuitive in parsecs than in light years. Although less familiar to the public, it is the preferred unit in scientific publications, planetary catalogs, and distance mapping of the Milky Way.