Convert Light Year to Mile
Convert light years to miles instantly. 1 light year = 5.878625e+12 mile — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Mile to Light Year converter for the reverse conversion.
Units explained
Light Year
A light year is the distance light travels in one Julian year in vacuum — exactly 9,460,730,472,580,800 meters (about 9.46×10¹⁵ m). It is the most common unit for expressing inter-stellar distances in non-technical astronomy.
Defined as the speed of light (299,792,458 m/s, exact) multiplied by one Julian year (365.25 days × 86400 seconds/day). Both factors are exact, making the light year exact by definition.
Light years are used in popular astronomy, science journalism, and stellar distance descriptions. The nearest star (Proxima Centauri) is 4.24 ly away; the Milky Way is about 100,000 ly across.
Concept of distance-as-time used since the 19th century; the modern exact definition follows from the 1983 SI definition of the meter via the speed of light.
Mile
A mile (statute mile) is an Imperial and US customary unit of length equal to 5,280 feet or exactly 1,609.344 meters. It is the standard unit for road distances in the United States and the United Kingdom.
The mile derives from the Roman mille passus ("thousand paces" — about 1,480 meters). The English statute mile was fixed at 5,280 feet by the Weights and Measures Act of 1593, and exactly defined as 1,609.344 m by the 1959 International Yard and Pound Agreement.
Miles are used in the US and UK for road signs, speed limits (mph), athletic events (one-mile run), and geographic distances. Aviation also uses statute miles for some visibility measurements.
Roman origin (mille passus); English statute mile fixed at 5,280 feet in 1593; standardized to 1,609.344 m exactly by the 1959 International Yard and Pound Agreement.
Light Year to Mile conversion formula
The relationship between light years and miles:
To convert light years to miles, multiply the value in light years by 5.878625e+12. To reverse, multiply miles by 1.701078e-13.
How to use this converter
Type a value into the calculator. The result in miles updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Mile to Light Year converter for the reverse direction.
Step-by-step: convert light years to miles
- Write down the value in light years (ly).
- Multiply that value by the factor 5.878625e+12.
- The product is the equivalent value in miles (mi).
- To reverse, multiply the mile value by 1.701078e-13.
Worked examples
Example 1 — Convert 1 ly to mi:
1 × 5.878625e+12 = 5.878625e+12 mi
Example 2 — Convert 100 ly to mi:
100 × 5.878625e+12 = 5.878625e+14 mi
Light Year to Mile conversion table
Standard reference values for converting light years to miles:
| Light Year [ly] | Mile [mi] |
|---|---|
| 0.01 | 5.878625e+10 |
| 0.1 | 5.878625e+11 |
| 1 | 5.878625e+12 |
| 2 | 1.175725e+13 |
| 3 | 1.763588e+13 |
| 4 | 2.35145e+13 |
| 5 | 2.939313e+13 |
| 10 | 5.878625e+13 |
| 20 | 1.175725e+14 |
| 30 | 1.763588e+14 |
| 40 | 2.35145e+14 |
| 50 | 2.939313e+14 |
| 100 | 5.878625e+14 |
| 500 | 2.939313e+15 |
| 1000 | 5.878625e+15 |
Frequently asked questions
How many miles is 1 light year?
How do I convert light years to miles?
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How many miles is 100 light years?
Popular length unit conversions
Convert Light Year to other length units
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Metric / SI (4 units)
Imperial / US Customary (4 units)
Astronomical (8 units)
Sources & references
Conversion factor (1 ly = 5.878625e+12 mi) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.