## Measurement unit: light second

**Full name:** light second

**Plural form:** light seconds

**Alternate spelling:** lightsecond

**Category type:** length

**Scale factor:** 299792458

## SI unit: metre

The SI base unit for length is the metre.

1 metre is equal to 3.3356409519815E-9 light second.

Valid units must be of the **length** type.

You can use this form to select from known units:

## 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.

## Sample conversions: light second