Light Year to Astronomical Unit Conversion Calculator: Free Online Tool
Convert light years to astronomical units with our free online length converter.
Light Year to Astronomical Unit Calculator
How to Use the Calculator:
- Enter the value you want to convert in the 'From' field (Light Year).
- The converted value in Astronomical Unit will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Length category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Light Year to Astronomical Unit
Converting Light Year to Astronomical Unit involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Light Year = 6.3242e+4 astronomical unitsExample Calculation:
Convert 10 light years: 10 × 6.3242e+4 = 6.3242e+5 astronomical units
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.
What is a Light Year and a Astronomical Unit?
A light-year is a unit of astronomical distance equal to the distance that light travels in one Julian year in a vacuum (approximately 9.461 trillion kilometers or 5.879 trillion miles).
An astronomical unit is a unit of length roughly equal to the average distance between Earth and the Sun. It is defined as exactly 149,597,870,700 meters.
Note: The Light Year is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Astronomical Unit belongs to the imperial/US customary system.
History of the Light Year and Astronomical Unit
The concept was first used by Friedrich Bessel in 1838 when measuring the distance to the star 61 Cygni.
Historically used to measure distances within the Solar System, its value was refined over centuries through astronomical observations. The exact definition was adopted by the IAU in 2012.
Common Uses for light years and astronomical units
Explore the typical applications for both Light Year (imperial/US) and Astronomical Unit (imperial/US) to understand their common contexts.
Common Uses for light years
- Measuring distances to stars and galaxies
- Expressing the vast scale of the universe in astronomy
Common Uses for astronomical units
- Measuring distances within the Solar System (e.g., planet orbits)
- Expressing distances to near-Earth objects
Frequently Asked Questions
Questions About Light Year (ly)
Is a light-year a unit of time or distance?
A light-year (ly) is a unit of distance, not time. It represents the distance light travels in one year.
How far is a light-year in kilometers and miles?
One light-year is approximately 9.461 trillion kilometers (9.461 x 10^12 km) or 5.879 trillion miles (5.879 x 10^12 mi).
What is the closest star to Earth in light-years?
Excluding the Sun, the closest star system to Earth is Alpha Centauri, which is about 4.37 light-years away.
About Astronomical Unit (AU)
Why use Astronomical Units instead of kilometers or miles?
Astronomical Units (AU) provide a more convenient scale for the vast distances within our solar system. Expressing interplanetary distances in km or miles results in extremely large and unwieldy numbers.
How many kilometers/miles is 1 AU?
1 Astronomical Unit (AU) is approximately 149.6 million kilometers or 93 million miles.
How long does it take light to travel 1 AU?
It takes sunlight approximately 8 minutes and 20 seconds to travel the distance of one Astronomical Unit from the Sun to the Earth.
Conversion Table: Light Year to Astronomical Unit
| Light Year (ly) | Astronomical Unit (AU) |
|---|---|
| 1 | 63,241.979 |
| 5 | 316,209.893 |
| 10 | 632,419.786 |
| 25 | 1,581,049.465 |
| 50 | 3,162,098.931 |
| 100 | 6,324,197.861 |
| 500 | 31,620,989.305 |
| 1,000 | 63,241,978.61 |
All Length Conversions
Other Units from Length
- Meter (m)
- Kilometer (km)
- Hectometer (hm)
- Decimeter (dm)
- Centimeter (cm)
- Millimeter (mm)
- Inch (in)
- Foot (ft)
- Yard (yd)
- Mile (mi)
- Nautical Mile (NM)
- Micrometer (μm)
- Nanometer (nm)
- Parsec (pc)
- Angstrom (Å)
- Point (Typography) (pt)
- Mil/Thou (mil)
- Fathom (fath)
- Furlong (fur)
- Link (Gunter's) (li)
- Pace (pace)
- Span (span)
- Digit (digit)
- Cable Length (cb)
- Ell (ell)
- Finger (finger)
- Roman Mile (m.p.)
- Stadion (stadion)
- Chi (Chinese) (chi)
- Shaku (Japanese) (shaku)
- Li (Chinese) (li)
- Toise (toise)
- Bolt (bolt)
- Rope (rope)
- Smoot (smoot)
- Sajene (sajene)
- Ken (ken)
- Wa (wa)
- Vara (vara)
- Aln (aln)
- Cubit (Royal/Egyptian) (cubit)
- Versta (versta)
- Arpent (arpent)
- Ri (Japanese) (ri)
- Klafter (klafter)
- Yojana (yojana)
- Skein (skein)