  We used the Navy Precision Optical Interferometer to measure the
limb-darkened angular diameter of the exoplanet host star kappa CrB and
obtained a value of 1.543 +/- 0.009 mas. We calculated its physical radius
(5.06 +/- 0.04 R_Sun) and used photometric measurements from the literature
with our diameter to determine kappa CrB's effective temperature (4788 +/- 17
K) and luminosity (12.13 +/- 0.09 L_Sun). We then placed the star on an H-R
diagram to ascertain the star's age (3.42 +0.32/-0.25 Gyr) and mass (1.47 +/-
0.04 M_Sun) using a metallicity of [Fe/H] = +0.15. With this mass, we
calculated the system's mass function with the orbital elements from a variety
of sources, which produced a range of planetary masses: m_p sin i = 1.61 to
1.88 M_Jup. We also updated the extent of the habitable zone for the system
using our new temperature.
