The most quoted mass for the Oort cloud is about 40 earth masses, estimated from the assumption that Halley's comet is a typical long period comet and the number of long period comets entering the solar system is (a) constant and (b) representative of the total population of the Oort cloud.

The upper limit to the mass is around that of Jupiter, the lower limit is 1-2 times the mass of the earth.

As a counter-question, was this the mass of the whole cometary halo outside the Edgworth-Kuiper belt or just the circularly symmetrical outer part? ie: what is the mass of the Hill's Cloud?