How many mm in 1 light-second?
The answer is 299792458000.
We assume you are converting between millimetre and light second.
You can view more details on each measurement unit: mm or
light-second
The SI base unit for length is the metre.
1 metre is equal to 1000 mm, or 3.3356409519815E-9 light-second.
Note that rounding errors may occur, so always check the results.
Use this page to learn how to convert between millimetres and light seconds.
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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.

››Definition: Light-second

A light-second is a unit of length. It is defined as the distance light travels in an absolute vacuum in one second or 299,792,458 meters. Note that this value is considered exact, since the meter is actually (as of 1983) defined in terms of the light second. It is just over 186,282 miles and almost 109 feet.

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