How many meters are in one light year?

Exactly 9,460,730,472,580,800 meters (about 9.461 × 10¹⁵ m), based on the International Astronomical Union definition of the light year as the distance light travels in one Julian year (365.25 days) in a vacuum.

What is a light year?

A light year is a unit of distance, not time. It is the total distance that light travels in one year through a vacuum — roughly 9.46 × 10¹⁵ meters or about 5.879 × 10¹² miles.

How accurate is this converter?

The converter uses the exact IAU value of 9,460,730,472,580,800 m per light year and JavaScript's 64-bit floating-point arithmetic. For values up to a few hundred light years the result is exact; for very large values (billions of light years) the last few digits may carry floating-point rounding.

What is an astronomical unit (AU)?

One AU is the mean distance from Earth to the Sun — exactly 149,597,870,700 meters. A single light year equals approximately 63,241 AU.

Can I convert fractions of a light year?

Yes. The input accepts any positive number, including decimals such as 0.5 or 4.22 (the distance to the nearest star, Proxima Centauri).

Light Years to Meters Converter

Enter a distance in light years and instantly get the exact equivalent in meters, kilometers, miles, and astronomical units.

Distance in Light Years

Enter any positive number (decimals accepted).

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Conversion Results

Enter a light year value to see the conversion.

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Summary

This converter transforms a distance expressed in light years into meters using the exact IAU definition: 1 light year = 9,460,730,472,580,800 meters. Results are shown in full integer form and in standard scientific notation. The tool also displays the equivalent distance in kilometers, miles, and astronomical units so you can compare cosmic scales at a glance.

How it works

Type a distance value (whole number or decimal) into the input field.
The converter multiplies your value by 9,460,730,472,580,800 m/ly (IAU definition).
The result is displayed in plain integer form and in scientific notation.
Equivalent values in kilometers, miles, and astronomical units appear below.
Click any "Copy" button to copy a result to your clipboard.

Use cases

Convert stellar distances from astronomy textbooks into SI meters.
Check the scale of interstellar travel in science-fiction scenarios.
Verify physics homework involving light-year unit conversions.
Compare light year distances to AU or miles for a human-scale perspective.
Generate precise scientific notation for reports and papers.
Explore cosmological distances like the width of the Milky Way (~100,000 ly).

Frequently Asked Questions

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