Light Year Converter

The converter uses 9.4607 x 10^12 km per light-year, the distance light travels in one year in a vacuum. Converting 1 light-year to kilometres shows 9.460700e+12, which is roughly 9.46 trillion kilometres.

One parsec is about 3.0857 x 10^13 km. Converting 1 parsec to light-years here returns 3.261598. A parsec is the distance at which one astronomical unit subtends an angle of one arcsecond.

One AU is 1.496 x 10^8 km, the mean distance between Earth and the Sun. It is the natural yardstick for gaps inside the Solar System, so 1 AU to kilometres reads 149600000.

Light-year, astronomical unit, parsec, kilometre, mile and metre. You can convert any pair in either direction, and the Swap button flips the from and to units instantly.

The display keeps plain digits for magnitudes that are easy to read, roughly from 0.0001 up to a billion, and switches to scientific notation outside that band. Plain values show up to eight significant figures, and scientific values show six digits after the point.

Every value is routed through kilometres and rounded to nine decimal places internally, so a round trip such as light-year to km and back returns the original number to high precision.

They use standard accepted factors: a light-year as 9.4607 x 10^12 km, a parsec as 3.0857 x 10^13 km and an AU as 1.496 x 10^8 km. The results are accurate to the significant figures shown, not to more digits than the factors carry.

Yes. The Copy button copies the full labelled line, for example 1 Parsec = 3.261598 Light-year, so you can paste both the value and its units.

No. The calculation runs entirely in your browser, so it is free, private and works offline once the page has loaded.