Light Year Converter · Astronomical Distance Unit Conversion

Convert light years to kilometers, meters, astronomical units, parsecs, miles and vice versa. Explore the vast scales of the universe with precision.

Enter Light Years

Light Years (ly)

Conversion Results

Light Years (ly) 1

Kilometers (km) 9,460,730,472,580.8

Meters (m) 9.460730e+15

Astronomical Units (AU) 63,241.077084

Parsecs (pc) 0.306601

Miles (mi) 5,878,625,373,183.61

Cosmic Scale ~ 1.00 ly — within range of the nearest star system.

Light Year Converter · User Guide & Astronomy Encyclopedia

What is a Light Year?

A light-year (ly) is an astronomical unit of distance that represents the distance light travels in one year in a vacuum.

Important clarification: A light-year is a unit of distance, not time!

How Many Kilometers in a Light Year?

1 light year = 9,460,730,472,580.8 km ≈ 9.46 × 10¹² km

Calculation:

Light speed c = 299,792.458 km/s
1 year (Julian) = 365.25 days = 31,557,600 seconds
1 light year = 299,792.458 × 31,557,600 = 9,460,730,472,580.8 km

Conversion Formulas

Light Year → Kilometers: ly × 9,460,730,472,580.8
Light Year → Meters: ly × 9,460,730,472,580,800
Light Year → AU: ly × 63,241.1
Light Year → Parsecs: ly × 0.306601
Light Year → Miles: ly × 5,878,625,373,183.6

Astronomical Distance Reference

Earth-Moon: ≈ 1.28 light-seconds
Earth-Sun: ≈ 8.3 light-minutes
Proxima Centauri: ≈ 4.22 ly
Milky Way diameter: ≈ 100,000 ly
Andromeda Galaxy: ≈ 2.54 million ly

How to Use

Select conversion mode
Enter the numeric value
Select the source unit if needed
Click the "Convert Now" button

Important Notes

This tool uses the IAU standard Julian year (365.25 days)
Extremely large numbers are displayed in scientific notation
Light-year measures distance, not time
All calculations are performed locally in your browser