1 Astronomical Unit to Light Year
Quick answer
1 Astronomical Unit (AU) equals
1.581251e-5 ly
To convert 1 Astronomical Units to Light Years, multiply by 1.581251e-5. Therefore, 1 Astronomical Unit (AU) equals 1.581251e-5 Light Year (ly).
Formula: ly = AU × 1.581251e-5. Calculation: 1 × 1.581251e-5 = 1.581251e-5 ly.
Convert Astronomical Unit (AU) to Light Year (ly) online with our free unit converter. In length, 1 AU = 1.581251e-5 ly. Explore step-by-step conversion steps, mathematical formulas, and quick conversion reference tables below.
Worked example: converting Astronomical Unit to Light Year
- Step 1 — start with the formula. ly = AU × 0.0000158125
- Step 2 — substitute your figure. 1 AU × 1.581251e-5
- Step 3 — read the result. 1 AU = 1.581251e-5 ly
- Step 4 — check it in reverse. AU = ly × 63,241.0770842663 returns 1 AU, which matches the figure you started with.
Length Converter
31 units available
1 AU = 1.581251e-5 ly
Formula:
ly = AU × 0.0000158125With your value: 1 AU = 1.581251e-5 ly
How big is that?
Everyday references on a logarithmic scale, all expressed in astronomical unit so you can sanity-check the result.
Other Astronomical Unit to Light Year conversions
Astronomical Unit to Light Year Conversion Table
| Astronomical Unit (AU) | Light Year (ly) |
|---|---|
| 0.5 | 7.906254e-6 |
| 1 | 1.581251e-5 |
| 2 | 3.162501e-5 |
| 5 | 7.906254e-5 |
| 10 | 0.000158 |
| 15 | 0.000237 |
| 20 | 0.000316 |
| 25 | 0.000395 |
| 50 | 0.000791 |
| 100 | 0.001581 |
| 250 | 0.003953 |
| 500 | 0.007906 |
| 1000 | 0.015813 |
Light Year to Astronomical Unit Conversion Table
| Light Year (ly) | Astronomical Unit (AU) |
|---|---|
| 0.5 | 31,620.538542 |
| 1 | 63,241.077084 |
| 2 | 126,482.154169 |
| 5 | 316,205.385421 |
| 10 | 632,410.770843 |
| 15 | 948,616.156264 |
| 20 | 1,264,821.541685 |
| 25 | 1,581,026.927107 |
| 50 | 3,162,053.854213 |
| 100 | 6,324,107.708427 |
| 250 | 15,810,269.271067 |
| 500 | 31,620,538.542133 |
| 1000 | 63,241,077.084266 |
Where these values come from
Every factor on this page is traced to the document that defines it. See the full provenance dataset or our methodology.
Astronomical Unit (AU)
Length
The astronomical unit is exactly 149 597 870 700 m (IAU Resolution B2, 2012).
Source: IAU Resolution B2 (2012) — definition of the astronomical unit; IAU B2 (2015) nominal values
International Astronomical Union · Reviewed 2026-07-01
Light Year (ly)
Length
A light-year is the distance light travels in one Julian year: 9 460 730 472 580 800 m exactly.
Source: IAU Resolution B2 (2012) — definition of the astronomical unit; IAU B2 (2015) nominal values
International Astronomical Union · Reviewed 2026-07-01
How to Convert Astronomical Unit to Light Year
To convert from Astronomical Unit (AU) to Light Year (ly), multiply the value by 1.581251e-5.
Formula: ly = AU × 0.0000158125
Reverse: AU = ly × 63,241.0770842663
Step-by-Step Example
- Start with your value in Astronomical Unit. For example: 5 AU
- Multiply by the conversion factor: 5 x 1.581251e-5
- The result is: 7.906254e-5 ly
Astronomical Unit and Light Year Relationship
Both Astronomical Unit and Light Year belong to the Astronomical system, making this an intra-system conversion within length. Since 1 Astronomical Unit represents a fraction of a Light Year (1 Light Year ≈ 6.324e+4 Astronomical Units), the Light Year is the larger measurement interval. Understanding the relationship between Astronomical Unit and Light Year is essential for accurate calculations in physics, engineering, commerce, and daily applications.
About Astronomical Unit
The astronomical unit (AU) is defined as exactly 149,597,870,700 metres, close to the mean Earth–Sun distance. It is the natural yardstick for the Solar System.
Common uses of Astronomical Unit: planetary science, orbital mechanics, astronomy.
About Light Year
A light year is the distance light travels through a vacuum in one Julian year — exactly 9,460,730,472,580,800 metres. It is a unit of distance, not of time.
Fun Fact: Proxima Centauri, the nearest star to the Sun, sits about 4.25 light years away.
Common uses of Light Year: astronomy, popular science, education.
Frequently Asked Questions
- What is 1 Astronomical Unit in Light Year?
- 1 Astronomical Unit equals 1.581251e-5 Light Year.
- How many Light Years are in 1 Astronomical Unit?
- There are exactly 1.581251e-5 Light Years in 1 Astronomical Unit. This means the conversion factor from Astronomical Unit to Light Year is 1.581251e-5.
- What is the formula to convert Astronomical Unit to Light Year?
- The formula to convert Astronomical Unit to Light Year is: ly = AU × 0.0000158125. For example, to convert 10 Astronomical Units to Light Years, you would multiply 10 by 1.581251e-5.
- What is a Astronomical Unit?
- The astronomical unit (AU) is defined as exactly 149,597,870,700 metres, close to the mean Earth–Sun distance. It is the natural yardstick for the Solar System.
- What is a Light Year?
- A light year is the distance light travels through a vacuum in one Julian year — exactly 9,460,730,472,580,800 metres. It is a unit of distance, not of time.
- What are the common uses of Astronomical Unit?
- The Astronomical Unit is commonly used in planetary science, orbital mechanics, astronomy.
Related Length Conversions
Cite this page
UnitConvertLab. (2026). 1 Astronomical Unit to Light Year. UnitConvertLab. Retrieved from https://unitconvertlab.com/convert/1-astronomical_unit-to-light_year