How to convert light-years to kilometers
- Take the value in light-years.
- Use the formula kilometers = light-years × 9,460,730,472,580.8.
- For example, 1 ly is 9,460,730,472,580.8 km.
About light-years and kilometers
A light-year is the distance light travels in a year. The IAU defines it with a year of 365.25 days and the exact speed of light, 299,792.458 km/s, which gives 9,460,730,472,580.8 km. So multiply light-years by about 9.461 trillion to get kilometers.
A light-year is a distance, not a time. Astronomers use it because kilometers become unreadable for stars: the nearest star beyond the Sun is about 40 trillion km away, which is easier to say as 4.2 light-years. Professional papers often use parsecs, which are 3.26 light-years.
Examples
- 1 ly (one light-year) is 9,460,730,472,580.8 km
- 4.25 ly (Proxima Centauri, the nearest star to the Sun) is 40,174,991,951,814.4 km
- 8.6 ly (Sirius, the brightest star in the night sky) is 81,362,282,064,194.9 km
- 2,500,000 ly (the Andromeda Galaxy, roughly) is 23,651,826,181,452,000,000 km
Light-years to kilometers chart
| Light-years (ly) | Kilometers (km) |
|---|---|
| 0.001 | 9,460,730,472.58 |
| 0.01 | 94,607,304,725.81 |
| 0.1 | 946,073,047,258.08 |
| 0.5 | 4,730,365,236,290.4 |
| 1 | 9,460,730,472,580.8 |
| 2 | 18,921,460,945,161.6 |
| 4.25 | 40,174,991,951,814.4 |
| 5 | 47,303,652,362,904 |
| 8.6 | 81,362,282,064,194.9 |
| Light-years (ly) | Kilometers (km) |
|---|---|
| 10 | 94,607,304,725,808 |
| 25 | 236,518,261,814,520 |
| 50 | 473,036,523,629,040 |
| 100 | 946,073,047,258,080 |
| 1,000 | 9,460,730,472,580,800 |
| 10,000 | 94,607,304,725,808,000 |
| 100,000 | 946,073,047,258,080,000 |
| 1,000,000 | 9,460,730,472,580,800,000 |
| 2,500,000 | 23,651,826,181,452,000,000 |