Kilometers to Parsecs (km to pc)

1 kilometer equals 3.240779289×10⁻¹⁴ parsecs (rounded).

1 kilometer = 3.240779289×10⁻¹⁴ parsecs

How to convert kilometers to parsecs

To convert kilometers to parsecs, multiply the number of kilometers by 3.240779289×10⁻¹⁴. The factor is rounded to 10 significant digits. To go the other way, multiply parsecs by 30,856,775,814,914 (rounded).

parsecs = kilometers × 3.240779289×10⁻¹⁴

Example: 10 kilometers = 3.240779289×10⁻¹³ parsecs.

About these units

Kilometer (km)

Metric (SI)Current unit

1,000 meters. The standard unit for road distances in most countries.

A name for 1,000 meters took a while to settle. In 1793 France's National Convention made the metre the sole French unit of length, and the first proposed name for the thousand-metre multiple was millaire. Everyday French usage then leaned on the myriametre, 10,000 meters, well into the 1800s. The Netherlands adopted the kilometre in 1817, under the local name mijl, and made it the only official unit of that size in 1867. In 1935 the CIPM dropped the myria- prefix, which left the kilometre as the standard unit for road-scale distances.

Kilo- is the SI prefix for a thousand, and the kilometre is now the preferred unit for land distances in most of the world, with the United States, the United Kingdom and Liberia among those that still use the mile. One kilometre is about 0.621 mile. The main span of Lisbon's 25 de Abril Bridge, at 1.013 km, gives a sense of the scale. Even its pronunciation has been argued over: in 1970 Australia's Metric Conversion Board made stress on the first syllable official, although Prime Minister Gough Whitlam argued for stress on the second. Military slang in several countries calls it a klick.

1 kilometer = 1,000 meters (exactly).

Sources: Wikipedia: Kilometre; Wikipedia: Metric prefix; BIPM: history of the metre

Parsec (pc)

AstronomicalCurrent unit

About 3.26 light-years, defined as 648,000/π astronomical units. The standard unit for distances to stars.

British astronomer Herbert Hall Turner coined the word in 1913 as a contraction of the distance at which a parallax equals one arcsecond. Rivals were Frank Dyson's astron and Carl Charlier's siriometer. The idea rests on stellar parallax, first measured successfully by Friedrich Bessel in 1838 for 61 Cygni, which he put near 3.5 parsecs. With the angle in arcseconds, the distance in parsecs is simply its reciprocal.

Since 2015 the IAU has defined the parsec as exactly 648,000 divided by pi astronomical units, which with the 2012 exact au gives about 30,856,775,814,913,673 meters, or 3.0857 times ten to the sixteenth power. That is roughly 3.26 light-years. Proxima Centauri lies about 1.3 parsecs away. Professional astronomers still prefer the parsec to the light-year, and ESA's Gaia satellite, launched in 2013, measures parallaxes to microarcsecond precision.

1 parsec = 3.085677581×10¹⁶ meters (approximately).

Sources: Wikipedia: Parsec; NIST SP 811 Appendix B.8: factors for units outside the SI

Related conversions

See all length units.