Convert parsec to light year

One parsec equals 3.261564 light years. To convert any number of parsecs to light years, multiply by 3.26156378.

The converter above works in both directions and updates as you type. Below you will find the formula, a worked example and a reference table of common values.

Length conversions come up wherever a measurement crosses a border: a height given in feet and inches on a form that wants centimetres, a running distance recorded in kilometres and compared against miles, a component specified in millimetres and ordered from a supplier working in inches. The conversions themselves are exact — the inch, foot, yard and mile have all been defined in metric terms since 1959 — so any discrepancy comes from rounding, not from the units disagreeing.

parsec to light year formula

To go the other way, use parsec = light year ÷ 3.26156378.

About these units

A parsec is the distance at which one astronomical unit subtends one arcsecond — about 3.26 light years. Astronomers prefer it because it falls directly out of parallax measurement.

A light year is the distance light travels in one Julian year, about 9.46 trillion kilometres. Despite the name it measures distance, not time.

Parsec is also written parsecs. Light Year is also written light years, lightyear and lightyears.

Sources

1. International Astronomical Union, Resolution B2 (2012), XXVIII General Assembly — the astronomical unit as exactly 149,597,870,700 m, and the Julian year of 365.25 days from which the light year and parsec follow.