The distance of the Virgo cluster is derived in the B band from the 21 cm-line width-absolute magnitude relation .
The latter is calibrated using 18 spirals with Cepheid distances mainly from HST .
The calibration is applied to a complete sample of non-peculiar spirals with i > 45 ^ { \circ } and lying within the optical ( n=49 ) or X-ray ( n=35 ) contour of the cluster , resulting in a mean cluster distance of ( m - M ) ^ { 0 } = 31 \fm 58 \pm 0 \fm 24 ( external error ) or 20.7 \pm 2.4 Mpc .
The mean distance of subcluster A is 0 \fm 46 \pm 0 \fm 18 smaller than that of subcluster B , but the individual distances of the members of the two substructures show considerable overlap .
Cluster spirals with 30 ^ { \circ } < i < 45 ^ { \circ } yield almost as good distances as more inclined galaxies .
H I-truncated galaxies are overluminous by 0 \fm 8 at a given line width .
The distance modulus is corrected by -0 \fm 07 for the fact that cluster members have lower H I-surface fluxes and are redder in ( B - I ) at a given line width than the ( field ) calibrators .
Different sources of the B magnitudes and line widths have little effect on the resulting distance .
Different precepts for the internal-absorption correction change the result by no more than \pm 0 \fm 17 .
The individual distances of the cluster members do not show any dependence on recession velocity , inclination , Hubble type or line width .
The dependence on apparent magnitude reflects the considerable depth effect of the cluster .
The adopted distance is in good agreement with independent distance determinations of the cluster .

Combining the cluster distance with the corrected cluster velocity of 1142 \pm 61 km s ^ { -1 } gives H _ { 0 } = 55 \pm 7 km s ^ { -1 } Mpc ^ { -1 } ( external error ) .
If the Virgo cluster distance is inserted into the tight Hubble diagram of clusters out to 11 000 km s ^ { -1 } using relative distances to the Virgo cluster one obtains a global value of H _ { 0 } = 57 \pm 7 km s ^ { -1 } Mpc ^ { -1 } .