  Inflation gives rise to a nearly scale-invariant spectrum of tensor
perturbations (gravitational waves), their contribution to the Cosmic
Background Radiation (CBR) anisotropy depends upon the present cosmological
parameters as well as inflationary parameters. The analysis of a
sampling-variance-limited CBR map offers the most promising means of detecting
tensor perturbations, but will require evaluation of the predicted multipole
spectrum for a very large number of cosmological parameter sets. We present
accurate polynomial formulae for computing the predicted variance of the
multipole moments in terms of the cosmological parameters $\Omega_\Lambda$,
$\Omega_0h^2$, $\Omega_B h^2$, $N_{\nu}$, and the power-law index $n_T$ which
are accurate to about 1\% for $l\le 50$ and to better than 3\% for $50< l \le
100$ (as compared to the numerical results of a Boltzmann code).
