[paul.fr]

Has or even can anyone calculate the mass of the universe or "just" our own solar system?

[DoctorBeaver]

Cosmologists/astrophysicists are constantly trying to calculate the total mass of the universe as that would answer the question about whether the universe will continue to expand forever or eventually contract into a Big Crunch. The problem is that it looks as though only a small fraction of the total mass is visible; the rest being dark matter.

The mass of galaxies, galaxy clusters & superclusters can be estimated by rotational velocity, & observations show that there is a lot of mass that we simply cannot see. This mass could be in the form of brown dwarves, MACHOS, black holes, intergalactic dust or gas etc. It could also be non-baryonic matter such as WIMPS.

The structure of the universe tends to indicate that most of the mass is in the form of cold dark matter.

However, as we can only see a small portion of the total universe, any estimate must assume that the overall distribution of matter in the universe is homogeneous. If that is not the case then we have absolutely no way of ever knowing.