  This paper introduces the calibration of the time-to-distance relation for
the BESIII drift chamber. The parameterization of the time-to-distance relation
is presented. The studies of left-right asymmetry and the variation with the
entrance angle are performed. The impact of dead channels on the
time-to-distance relation is given special attention in order to reduce the
shifts of the measured momenta for the tracks passing near dead cells. Finally
we present the spatial resolution (123 {\mu}m) for barrel Bhabha events
(|cos{\theta}|<0.8) from J/{\psi} data taken in 2012.
