---
title: "Light-years to Millimeters — ly to mm converter"
description: "1 light-year = 9.4607305 × 10^18 millimeters. Convert light-years to millimeters with a full conversion table, the exact formula, and a calculator for any value."
url: https://atoneplace.net/convert/light-years-to-mm/
site: "At One Place"
---

# Light-years to millimeters

**1 light-year in millimeters: 1 ly = 9.4607305 × 10^18 mm**

mm = ly × 9.460730473 × 10^18

To convert light-years to millimeters, multiply by 9.460730473 × 10^18. The table below gives the values people look up most often, and the converter works for any number.

## Light-years to millimeters table

*Common light-year values converted to millimeters.*

| Light-years | Millimeters |
| --- | --- |
| 1 ly | 9.4607305 × 10^18 |
| 2 ly | 1.8921461 × 10^19 |
| 3 ly | 2.8382191 × 10^19 |
| 4 ly | 3.7842922 × 10^19 |
| 5 ly | 4.7303652 × 10^19 |
| 10 ly | 9.4607305 × 10^19 |
| 15 ly | 1.4191096 × 10^20 |
| 20 ly | 1.8921461 × 10^20 |
| 25 ly | 2.3651826 × 10^20 |
| 30 ly | 2.8382191 × 10^20 |
| 40 ly | 3.7842922 × 10^20 |
| 50 ly | 4.7303652 × 10^20 |
| 75 ly | 7.0955479 × 10^20 |
| 100 ly | 9.4607305 × 10^20 |
| 250 ly | 2.3651826 × 10^21 |
| 500 ly | 4.7303652 × 10^21 |
| 1,000 ly | 9.4607305 × 10^21 |

## How the conversion works

The relationship is mm = ly × 9.460730473 × 10^18. Both units measure length, so the conversion is a fixed factor that never changes.

## Common questions

### How many millimeters are in one light-year?

One light-year equals 9.4607305 × 10^18 millimeters. mm = ly × 9.460730473 × 10^18.

### How do you convert light-years to millimeters?

Use mm = ly × 9.460730473 × 10^18. So 10 ly is 9.4607305 × 10^19 mm.

### How many light-years are in one millimeter?

One millimeter equals 1.057 × 10^-19 light-years, which is the reverse of the conversion above.

## Related pages

- [Millimeters to Light-years](https://atoneplace.net/convert/mm-to-light-years/)
- [Light-years to Meters](https://atoneplace.net/convert/light-years-to-meters/)
- [Light-years to Kilometers](https://atoneplace.net/convert/light-years-to-km/)
- [Light-years to Centimeters](https://atoneplace.net/convert/light-years-to-cm/)
- [Light-years to Miles](https://atoneplace.net/convert/light-years-to-miles/)
- [Light-years to Yards](https://atoneplace.net/convert/light-years-to-yards/)
- [Light-years to Feet](https://atoneplace.net/convert/light-years-to-feet/)
- [Light-years to Inches](https://atoneplace.net/convert/light-years-to-inches/)

## Sources

- Guide for the Use of the International System of Units (SP 811) — NIST (https://www.nist.gov/pml/special-publication-811) [Public domain (US Government)]
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures (https://www.bipm.org/en/publications/si-brochure)
- Calculated on this page — At One Place (/about/)