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megametre millimetre |
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light year |

How many mm in 1 light year?
The answer is 9.46073047258E+18.

We assume you are converting between **millimetre** and **light year**.

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light year

The SI base unit for **length** is the metre.

1 metre is equal to 1000 mm, or 1.05700083402E-16 light year.

Note that rounding errors may occur, so always check the results.

Use this page to learn how to convert between millimetres and light years.

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A millimetre (American spelling: millimeter, symbol mm) is one thousandth of a metre, which is the International System of Units (SI) base unit of length. The millimetre is part of a metric system. A corresponding unit of area is the square millimetre and a corresponding unit of volume is the cubic millimetre.

A light year, abbreviated ly, is the distance light travels in one year: roughly 9.46 × 1012 kilometres (9.46 petametres, or about 5.88 × 1012 (nearly six trillion) miles). More specifically, a light year is defined as the distance that a photon would travel, in free space and infinitely far away from any gravitational or magnetic fields, in one Julian year (365.25 days of 86400 seconds each).

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