The redshift z is defined by:
z = (L - Lo)/Lo
where Lo is the wavelength at rest, and L is the red shifted wavelength.
The relationship between the redshift z and the distance d is given by the following formaula:
d = (c/Ho) x [(1 + z)2 - 1] / [(1 + z)2 + 1]
where c = 3x1010 cm/sec is the velocity of light, and Ho = 71 (km/sec)/Mpc is the Hubble constant.