Parsec Converter
Convert parsecs to light-years, kiloparsecs, megaparsecs, AU, kilometres, and miles using the exact IAU definition 1 pc = 3.0856775814913673 × 10¹⁶ m.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
Formula
1 pc = 3.0856775814913673 × 10¹⁶ m = 3.26156 ly = 206,265 AU
1 parsec is the distance at which 1 AU subtends 1 arcsecond of parallax. 1 pc ≈ 3.26 light-years.
This tool provides educational conversions of astronomical distances only. It is not a navigation, mission-planning, or ephemeris service. For professional or spacecraft work, use official IAU, NASA, or observatory data products.
About the Parsec Converter
The parsec converter changes distances between parsecs, light-years, astronomical units and kilometres. A parsec is the distance at which one astronomical unit subtends an angle of one arcsecond — about 3.26 light-years or 206,265 AU. Professional astronomers use parsecs because they follow directly from parallax measurements, while light-years are more common in popular science, so converting between them is a frequent need.
How to use it
- 1Choose the unit you already have (pc, kpc, Mpc, ly, AU, km, m, or mi).
- 2Enter the distance value.
- 3Select the target unit and press Convert.
- 4Read the full equivalence table for all supported units.
Worked example
1 parsec = 3.26156 light-years = 206,265 AU = 3.086 × 10¹³ km. The Andromeda Galaxy at about 0.78 Mpc is roughly 2.54 million light-years away.
How it works
What is a parsec?
A parsec (pc) is the distance at which 1 astronomical unit subtends an angle of 1 arcsecond. By geometry, 1 pc = AU ÷ tan(1″) = 3.0856775814913673 × 10¹⁶ m.
Key equivalents
- 1 pc = 3.26156 light-years
- 1 pc = 206,265 AU
- 1 pc = 3.0857 × 10¹³ km
- 1 Mpc = 1,000,000 pc
Who it is for
Astronomy students, amateur astronomers, and science writers working with stellar and galactic distances.
Why it helps
Parsecs are the standard professional unit for stellar and galactic distances — converting them to light-years or kilometres makes the scale understandable.
Common use cases
- Converting stellar distances from parallax measurements
- Expressing galaxy separations in megaparsecs for Hubble law work
- Translating professional astronomy papers for general audiences
- Comparing parsec, light-year, and AU scales in coursework
Tips for better results
- Use parsecs or kiloparsecs for stars and the Milky Way; megaparsecs for galaxies.
- 1 pc ≈ 3.26 ly is a handy conversion to remember.
- Scientific notation appears automatically for very large or small results.
- The parsec is defined geometrically from parallax, not from the speed of light.
Common mistakes to avoid
- Confusing parsecs with light-years — 1 pc ≈ 3.26 ly, not 1:1.
- Mixing kiloparsecs and megaparsecs by a factor of 1000.
- Forgetting that 1 pc = 206,265 AU, a useful cross-check.
Frequently asked questions
A:1 parsec equals about 3.26156 light-years. It is the distance at which 1 AU subtends 1 arcsecond of parallax.
A:Parsecs arise naturally from parallax measurements — the most direct way to measure stellar distances — so they are the standard unit in professional astronomy.
A:One parsec contains 206,265 astronomical units, derived from 1 ÷ tan(1 arcsecond).
A:Yes. It runs in your browser on CalcWisee with no sign-up required.
Reviewed for accuracy · Last updated October 7, 2026
The astronomical unit is taken as exactly 149,597,870,700 metres per the IAU 2012 definition. Related light-time and light-year factors use the defined speed of light and the IAU Julian year where applicable.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
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