Light-Year to Kilometres Converter Formula
Understand the math behind the light-year to kilometres converter. Each variable explained with a worked example.
Formulas Used
Kilometres
km = light_years * 9460730472580.8Astronomical Units
au = light_years * 63241.077Parsecs
parsec = light_years / 3.26156Variables
| Variable | Description | Default |
|---|---|---|
light_years | Distance(ly) | 1 |
How It Works
Light-Year Conversion
A light-year is the distance light travels in one Julian year (365.25 days).
1 ly = 9 460 730 472 580.8 km
From: c × t = 299 792.458 km/s × 31 557 600 s
Worked Example
Proxima Centauri is about 4.246 ly away.
light_years = 4.246
- 01km = 4.246 × 9 460 730 472 580.8
- 02≈ 4.017 × 10¹³ km
- 03AU = 4.246 × 63241 ≈ 268 521 AU
- 04pc = 4.246 / 3.2616 ≈ 1.302 pc
Frequently Asked Questions
Is a light-year a unit of time or distance?
Distance. It measures how far light travels in one year.
Why do astronomers use parsecs too?
Parsecs arise naturally from the parallax method and are preferred in professional astronomy. 1 pc ≈ 3.262 ly.
How far is the nearest star?
Proxima Centauri: about 4.246 ly or 40.2 trillion km.
Ready to run the numbers?
Open Light-Year to Kilometres Converter