  We supply fitting formulae enabling the normalization of slow-roll inflation
models to the four-year COBE data. We fully include the effect of the
gravitational wave modes, including the predicted relation of the amplitude of
these modes to that of the density perturbations. We provide the normalization
of the matter power spectrum, which can be directly used for large-scale
structure studies. The normalization for tilted spectra is a special case. We
also provide fitting functions for the inflationary energy scale of
COBE-normalized models and discuss the validity of approximating the spectra by
power-laws. In an Appendix, we extend our analysis to include models with a
cosmological constant, both with and without gravitational waves.
