  We present new calibrations of far-ultraviolet (FUV) attenuation as derived
from the total infrared to FUV luminosity ratio (IRX) and the FUV-NUV color. We
find that the IRX-corrected FUV luminosities are tightly and linearly
correlated with the attenuation-corrected H\alpha\ luminosities (as measured
from the Balmer decrement), with a rms scatter of $\pm 0.09$ dex. The ratios of
these attenuation-corrected FUV to H\alpha\ luminosities are consistent with
evolutionary synthesis model predictions, assuming a constant star formation
rate over 100 Myr, solar metallicity and either a Salpeter or a Kroupa IMF with
lower and upper mass limits of 0.1 and 100\msun. The IRX-corrected FUV to
Balmer-corrected H\alpha\ luminosity ratios do not show any trend with other
galactic properties over the ranges covered by our sample objects. In contrast,
FUV attenuation derived from the FUV-NUV color (UV spectral slope) show much
larger random and systematic uncertainties. When compared to either
Balmer-corrected H\alpha\ luminosities or IRX-corrected FUV luminosities the
color-corrected FUV luminosities show $\sim 2.5$ times larger rms scatter, and
systematic nonlinear deviations as functions of luminosity and other
parameters. Linear combinations of 25um and 1.4GHz radio continuum luminosities
with the observed FUV luminosities are also well correlated with the
Balmer-corrected H\alpha\ luminosities. These results provide useful
prescriptions for deriving attenuation-corrected star formation rates of
galaxies based on linear combinations of UV and IR or radio luminosities, which
are presented in convenient tabular form. Comparisons of our calibrations with
attenuation corrections in the literature and with dust attenuation laws are
also made.
