# Light-second conversions

The light-second conversion selector on this page selects the length/distance measurement unit to convert to starting from light-seconds. To make a conversion starting from a unit of length other than light-second, simply click on the "Reset" button.

## About light-second

The **light-second**, or **light second**, is a unit of distance defined as the distance that light travels in free space (or vacuum) in one second.

The light-second is equal to 299.792458 × 10^{6} meters (1 light-second = 299.792458 × 10^{6} m), the base unit of length in the International System of Units (SI). The light-second is also equal to 299.792458 × 10^{3} kilometers (km) (an SI unit of length), or approximately 186.28 × 10^{3} miles (mi) or 983.57 × 10^{6} feet (ft), which are US customary / Imperial units of length.

The light-second is used in astronomy, relativistic physics and telecommunications. Common astronomical measurement units include the parsec (1 light-second ≈ 9.7156 × 10^{-9} pc), the astronomical unit (1 light-second = 2.0040 × 10^{-3} AU) and the light-year (1 light-second = 31.688 × 10^{-9} ly).

Plural: light-seconds