Light-Year Distance Converter
Convert a distance in light-years to kilometres, miles, astronomical units, and parsecs. This browser-only converter uses standard astronomy definitions and makes clear that a light-year measures distance, not time.
A Light-Year Is a Distance
A light-year is the distance light travels in one year, not a measure of time. NASA describes it as about 9.46 trillion kilometres or 5.88 trillion miles.
This converter starts with light-years and shows the same distance in kilometres, miles, astronomical units, and parsecs.
Why Four Units?
Kilometres and miles help make a large distance legible outside astronomy. Astronomical units describe solar-system scale: one au is the defined Sun–Earth distance unit.
Parsecs are commonly used by astronomers for stellar and galactic distances. One parsec is a little more than 3.26 light-years.
Reading Large Results
Large astronomical distances are shown as full numbers with digit grouping, so you can read and copy them without translating scientific notation.
The values are unit conversions, not travel times or estimates of an object's current position.
Examples
Nearest star system scale
Input
4.2465 ly
Show result
Result
About 40,167,000,000,000 km and 1.30 pc
Proxima Centauri is roughly this far away.
One light-year
Input
1 ly
Show result
Result
9,460,730,472,580.8 km, 5,878,625,373,183.6 mi, about 63,241 au, and 0.3066 pc
A galaxy-scale distance
Input
1,000,000 ly
Show result
Result
About 306,601 pc
The converter groups large numbers with commas for readability.
Frequently Asked Questions
Is a light-year a time measurement?
No. It is the distance light travels in one year.
What is an astronomical unit?
An astronomical unit, written au, is a defined length equal to 149,597,870,700 metres exactly.
What is a parsec?
A parsec is an astronomical distance unit defined from the astronomical unit; it is about 3.26 light-years.
Are results stored?
No. The calculation happens in your browser and is not uploaded or stored.
References
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