light-years to miles Converter
Convert light-years to miles instantly. Includes a reference table and formula.
| light-years | miles |
|---|
How to convert light-years to miles
Enter your value
Type the number of light-years you want to convert into the left box. The result in miles appears instantly in the right box. You can also type into the right box to convert in the other direction.
Use the swap button
Click the ⇄ Swap button to reverse the conversion — miles to light-years. Your current value carries across so you don't have to re-enter anything.
Why light-years measure distance, not time
Despite the name, a light-year is a unit of distance: the distance light travels through a vacuum in one Julian year (365.25 days), at light's constant speed of 299,792,458 metres per second. Astronomers use it instead of miles or kilometres because interstellar distances expressed in those units produce impractically large, hard-to-compare numbers — 1 light-year is about 5.879 trillion miles, a figure that would otherwise need to be written out in full every time.
Light-years in context
The nearest star to Earth
Proxima Centauri, the closest star to our Sun, is about 4.24 light-years away — roughly 24.9 trillion miles. Light you could observe from it tonight left the star over 4 years ago, meaning you're always seeing it as it was in the past, not as it is now.
How slow spacecraft are by comparison
Voyager 1, humanity's fastest and most distant spacecraft, travels at roughly 38,000 mph — yet it would take about 17,700 years to cover a single light-year. This is why light-years, not miles, are the practical unit for describing distances beyond the solar system.
Related astronomical units
Astronomers also use the astronomical unit (AU, the Earth-Sun distance, about 93 million miles) for solar-system-scale distances, and the parsec (about 3.26 light-years) for larger cosmic distances — light-years sit in between, most commonly used for distances to nearby stars and within our galaxy.
| light-years | miles |
|---|---|
| 0.0001 | 5.879e+08 |
| 0.001 | 5.879e+09 |
| 0.01 | 5.879e+10 |
| 0.1 | 5.879e+11 |
| 1 | 5.879e+12 |
| 4.24 | 2.493e+13 |
Frequently asked questions
How do I convert light-years to miles?
To convert light-years to miles, multiply by 5879000000000.0. Or use the calculator above for instant results.
How many miles are in 1 light-year?
1 light-year equals approximately 5,879,000,000,000 miles (about 5.879 trillion miles).
Is the light-years to miles converter free?
Yes, the light-years to miles converter is completely free with no sign-up required, no downloads, and it works offline once the page has loaded.
Is a light-year a measure of time or distance?
Despite the name, a light-year is a measure of distance — the distance light travels in one Julian year (365.25 days) at 299,792,458 metres per second. Astronomers use it because interstellar distances in miles produce impractically large numbers.
How far away is the nearest star to Earth in light-years?
Proxima Centauri, the nearest star to the Sun, is about 4.24 light-years away — roughly 24.9 trillion miles.
How long would it take a spacecraft to travel one light-year?
At Voyager 1's speed (roughly 38,000 mph, humanity's fastest spacecraft), it would take about 17,700 years to cover one light-year.