  We present accurate resolved $WISE$ photometry of galaxies in the combined
SINGS and KINGFISH sample. The luminosities in the W3 12$\mu$m and W4 23$\mu$m
bands are calibrated to star formation rates (SFRs) derived using the total
infrared luminosity, avoiding UV/optical uncertainties due to dust extinction
corrections. The W3 relation has a 1-$\sigma$ scatter of 0.15 dex over nearly 5
orders of magnitude in SFR and 12$\mu$m luminosity, and a range in host stellar
mass from dwarf (10$^7$ M$_\odot$) to $\sim3\times$M$_\star$ (10$^{11.5}$
M$_\odot$) galaxies. In the absence of deep silicate absorption features and
powerful active galactic nuclei, we expect this to be a reliable SFR indicator
chiefly due to the broad nature of the W3 band. By contrast the W4 SFR relation
shows more scatter (1-$\sigma =$ 0.18 dex). Both relations show reasonable
agreement with radio continuum-derived SFRs and excellent accordance with
so-called "hybrid" H$\alpha + 24 \mu$m and FUV$+$24$\mu$m indicators. Moreover,
the $WISE$ SFR relations appear to be insensitive to the metallicity range in
the sample. We also compare our results with IRAS-selected luminous infrared
galaxies, showing that the $WISE$ relations maintain concordance, but
systematically deviate for the most extreme galaxies. Given the all-sky
coverage of $WISE$ and the performance of the W3 band as a SFR indicator, the
$L_{12\mu \rm m}$ SFR relation could be of great use to studies of nearby
galaxies and forthcoming large area surveys at optical and radio wavelengths.
