Redshift Velocity Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Reading recession speed from stretched light
Redshift measures how much light from a receding object has been stretched to longer, redder wavelengths - at low redshift values, this stretching relates to recession velocity through a simple linear relationship.
Worked example
For a redshift of z = 0.01:
v = 299,792.458 x 0.01 = 2,997.92 km/s
This simplified formula (v = cz) only holds accurately at low redshift, generally below about z = 0.1 - at higher redshifts, where recession velocities approach a significant fraction of the speed of light, the full relativistic Doppler formula must be used instead, since velocity cannot simply scale linearly all the way up to or past the speed of light.