  We present the results of a numerical calculation of the photon splitting
rate below the electron-pair creation threshold ($\omega \le 2m$) in magnetic
fields $B ~{> \atop \sim}~ B_{\rm cr} = m^2 /e = 4.414 \times 10^{9}$ T. Our
results confirm asymptotic approximations derived in the low-field ($B < B_{\rm
cr}$) and high-field ($B \gg B_{\rm cr}$) limit, and allow interpolating
between the two asymptotic regions. Our expression for the photon splitting
rate is a simplified version of a formula given by Mentzel et al. We also point
out that, although the analytical formula is correct, the splitting rates
calculated there are wrong due to an error in the numerical calculations.
