How many miles are in a light year?

One light year equals approximately 5,878,625,373,183.6 miles — roughly 5.879 trillion miles. This is the distance light travels in one Julian year (365.25 days) through a vacuum at 186,282.397 miles per second.

How many light years are in a mile?

One mile equals approximately 1.70108 × 10⁻¹³ light years. In other words, a mile is an almost invisibly tiny fraction of a light year on the astronomical scale.

What is a light year?

A light year (ly) is the distance light travels in one Julian year (365.25 days) in a vacuum, moving at exactly 299,792,458 meters per second (about 186,282 miles per second). It equals approximately 9.461 × 10¹² kilometers or 5.879 × 10¹² miles.

How far is Proxima Centauri in miles?

Proxima Centauri, the nearest star to our Sun at about 4.2441 light years away, is roughly 24.9 trillion miles (2.49 × 10¹³ miles) from Earth.

What is the difference between a light year and an astronomical unit (AU)?

An astronomical unit (AU) is the average Earth-to-Sun distance — about 93 million miles (149.6 million km). One light year equals approximately 63,241 AU, making the light year far larger. The AU is typically used for distances within our solar system, while the light year is used for interstellar distances.

Why is scientific notation used for the results?

Astronomical distances expressed in miles involve extremely large numbers (e.g. 1 light year ≈ 5,878,625,373,183.6 miles) or extremely small ones for the reverse (1 mile ≈ 0.00000000000017 light years). Scientific notation like 5.879 × 10¹² is more compact and easier to read and compare.

Light Years to Miles Converter

Enter a distance in light years (or miles) and instantly see the equivalent in miles (or light years) along with related units.

Convert Distance

Light Years (ly)

Quick examples

Miles (mi)

Scientific notation

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Plain decimal

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Related Units

Kilometers (km) —

Astronomical Units (AU) —

Light Minutes —

Parsecs (pc) —

Light Year Reference Table

Click any row to load that distance into the converter above (ly → mi direction).

Object / Distance	Light Years (ly)	Miles (mi)
1 light minute	1/525,960 ly	1.118 × 10⁷ mi
1 light hour	1/8,766 ly	6.706 × 10⁸ mi
1 light day	~0.00274 ly	1.609 × 10¹⁰ mi
1 light year	1 ly	5.879 × 10¹² mi
Proxima Centauri	4.2441 ly	2.495 × 10¹³ mi
Alpha Centauri A/B	4.37 ly	2.569 × 10¹³ mi
Sirius	8.6 ly	5.056 × 10¹³ mi
Epsilon Eridani	10.5 ly	6.173 × 10¹³ mi
Vega	25 ly	1.470 × 10¹⁴ mi
Galactic Center	~26,000 ly	1.528 × 10¹⁷ mi
Milky Way diameter	~100,000 ly	5.879 × 10¹⁷ mi
Andromeda Galaxy	~2.537 million ly	1.491 × 10¹⁹ mi

Summary

This tool converts distances between light years and miles using the exact value: 1 light year = 5,878,625,373,183.6 miles (approximately 5.879 trillion miles). You can convert in either direction — enter light years to get miles, or enter miles to get light years. Results are shown in both standard and scientific notation so very large or very small values remain easy to read. All computation happens instantly in your browser with no server calls.

How it works

Choose a conversion direction: light years to miles, or miles to light years.
Enter your distance value in the input field.
The converter applies the exact IAU-derived factor: 1 ly = 5,878,625,373,183.6 miles.
The primary result appears in both plain decimal and scientific notation.
Related units — kilometers, astronomical units (AU), and light minutes — are shown below.
Use the Copy button to copy the result to your clipboard.

Use cases

Convert the distance to nearby stars (like Proxima Centauri at 4.24 ly) into miles.
Understand how far light travels in a year expressed in familiar mile units.
Check published astronomical distances for physics or astronomy assignments.
Explore the scale of the Milky Way or observable universe in miles.
Teaching aid for demonstrating the vastness of interstellar space.
Verify unit conversions in scientific papers or textbooks.
Convert spacecraft travel distances or mission planning figures.
Compare distances from science fiction (parsecs, light years) to real-world units.

Frequently Asked Questions

Last updated: 2026-10-05 · Reviewed by Nham Vu