Redshift, written as z, is the fractional stretch of a spectral line as a source moves away from us, and it is the single most important number in extragalactic astronomy. At small values the recession velocity is simply z times the speed of light, but as z grows the naive formula overshoots and you must use the relativistic Doppler expression, which keeps the velocity below the speed of light no matter how large z gets. This calculator reports both results in kilometers per second and as a fraction of light speed, so you can see where the simple approximation breaks down. Enter your measured z below. All computation runs in your browser with nothing sent to a server.
Redshift, written as z, is the fractional stretch of a spectral line as a source moves away from us, and it is the single most important number in extragalactic astronomy. At small values the recession velocity is simply z times the speed of light, but as z grows the naive formula overshoots and you must use the relativistic Doppler expression, which keeps the velocity below the speed of light no matter how large z gets.
Yes. Redshift Velocity Calculator is completely free, with no sign-up and no usage limits.
Yes. Redshift Velocity Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Redshift Velocity Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.