Parsec Converter
The parsec converter converts between parsecs and all other common astronomical distance units: light-years, astronomical units (AU), meters, kilometers, and miles. The parsec is the fundamental distance unit in stellar astronomy, defined as the distance at which one astronomical unit subtends an angle of one arcsecond. It connects directly to the parallax measurement technique. The astronomical unit is the exact IAU 2012 value of 149,597,870,700 meters. The light-year is calculated from the exact speed of light (299,792,458 m/s) and the Julian year (365.25 days). Enter a distance in any unit to see all conversions instantly.
Exact conversion factors (IAU 2012 / BIPM)
1 pc = 3.085677581e16 m (exactly)
1 ly = 9.4607304725808e15 m
1 AU = 149,597,870,700 m (exactly)
1 pc = 3.261563777 ly
1 pc = 206,264.806 AU
Prefix scale
- 1 milliparsec (mpc) = 0.001 pc = 3.26 light-years
- 1 parsec (pc) = 3.26 light-years
- 1 kiloparsec (kpc) = 1,000 pc = 3,261 light-years
- 1 megaparsec (Mpc) = 10^6 pc = 3.26 million light-years
- 1 gigaparsec (Gpc) = 10^9 pc = 3.26 billion light-years
Parsec: frequently asked questions
What is a parsec?
A parsec (pc) is the distance at which 1 astronomical unit (AU) subtends an angle of 1 arcsecond. From trigonometry: 1 pc = 1 AU / tan(1 arcsecond) = 1 AU / (1/206,265) = 206,265 AU. In SI units: 1 pc = 3.085677581e16 m = 3.261563777 light-years. Parsecs are the standard unit in stellar and galactic astronomy because they derive directly from parallax measurements.
What is an astronomical unit (AU)?
An astronomical unit (AU) is the mean distance from Earth to the Sun: 1 AU = 149,597,870,700 m (exactly, by IAU 2012 definition). It is the natural distance scale for the Solar System. Mars orbits at 1.524 AU; Jupiter at 5.203 AU; Neptune at 30.07 AU. The Oort Cloud extends to roughly 100,000 AU.
How is a parsec defined via parallax?
A star at 1 parsec shows an annual parallax of 1 arcsecond (the apparent shift in position against background stars as Earth moves from one side of its orbit to the other, 2 AU total). Stars are too far away for 1 arcsecond parallaxes; the nearest star (Proxima Centauri) shows a parallax of 0.7687 arcseconds, placing it at 1/0.7687 = 1.30 pc = 4.24 light-years.
What is the difference between a parsec and a light-year?
Both measure astronomical distances, but a parsec is slightly larger: 1 pc = 3.2616 light-years. Parsecs are preferred by professional astronomers because they relate directly to parallax (the observational quantity). Light-years are more intuitive for the public and are often used in popular science writing. Neither is a unit of time: a light-year is the distance light travels in one year, not a duration.
What are the large-scale distance units?
1 kiloparsec (kpc) = 1,000 pc = 3,261 light-years. 1 megaparsec (Mpc) = 10^6 pc = 3.261 million light-years. 1 gigaparsec (Gpc) = 10^9 pc. The Milky Way is about 30 kpc in diameter. The Andromeda Galaxy is 0.785 Mpc away. The observable universe is about 14.3 Gpc (46.5 billion light-years) in radius.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.