Light Year Converter
Convert light-years to kilometres, miles, astronomical units, parsecs, and more using the IAU Julian light-year (9.461 × 10¹⁵ m).
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
1 Light-years (ly) = 9.460730e+12 Kilometres (km)
Base: 1 ly = 9.4607304725808 × 10¹⁵ m (IAU Julian light-year)
This tool provides general unit conversions for everyday and educational use. For regulated, legal, or scientific applications, verify conversion factors against the applicable official standard.
About the Light Year Converter
The light year converter changes astronomical distances between light-years, kilometres, miles, astronomical units and parsecs, as well as light-days and light-hours. A light-year is the distance light travels in a Julian year — about 9.461 trillion kilometres — so it measures distance, not time. The tool helps put the distances to stars and galaxies into familiar units.
How to use it
- 1Type the value you want to convert.
- 2Choose the unit you are converting from and the unit you want (for example light-years to kilometres).
- 3The result updates as you type; use the swap button to reverse the direction.
- 4Copy or share the result with the buttons below it.
Worked example
Proxima Centauri, about 4.24 light-years away, is roughly 4.01 × 10¹³ km away, or about 1.30 parsecs.
How it works
What is a light-year?
A light-year is the distance light travels in a Julian year (365.25 days) in a vacuum: 9,460,730,472,580,800 metres exactly.
Key reference values
- 1 ly ≈ 9.461 × 10¹² km
- 1 ly ≈ 5.879 × 10¹² miles
- 1 ly = 63,241 AU
- 1 ly ≈ 0.3066 parsecs
Common use cases
- Converting star distances between light-years and parsecs
- Astronomy homework
- Understanding distances in science news
Frequently asked questions
A:No — it is a unit of distance, approximately 9.46 trillion kilometres.
A:Proxima Centauri is about 4.24 light-years from Earth.
Reviewed for accuracy · Last updated October 7, 2026
Conversion factors are based on internationally defined SI units and standard metric/imperial equivalence tables.
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.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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