Light-Year Calculator (Distance and Travel Time)
Enter a distance in light-years and a travel speed.
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Light-Year Calculator (Distance and Travel Time) by TheCalcTools
How the Light-Year Calculator (Distance and Travel Time) works
A light-year is the distance light travels in one Julian year (365.25 days): 9,460,730,472,580.8 km exactly. The astronomical unit (Earth–Sun average distance) is defined as 149,597,870.7 km and a parsec is about 3.26 light-years.
Even the nearest star is so far that a spacecraft at Voyager’s speed would take tens of thousands of years to get there.
The formula
Worked example
Using the default values shown in the calculator:
| Distance (light-years) | 4.2465 |
|---|---|
| Spacecraft speed (km/s) | 17 |
- Proxima Centauri is 40175000000000 km away, or 1.3020 parsecs.
- At 17 km/s the trip would take about 74,886 years.
Result:
| Kilometres | 40175000000000 |
|---|---|
| Miles | 24963600000000 |
| Astronomical units | 268,553 |
| Parsecs | 1.3020 |
| Travel time at that speed (years) | 74,886 |
Frequently asked questions
Is a light-year a unit of time?
No, it is a distance. It is the distance light covers in a year.
Sources and further reading
- Wikipedia: Light-year
- IAU: Resolution B2 (2012) on the astronomical unit and B3 (2015) on nominal solar values
- Wikipedia: Parsec
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.