# What is the expected size of primordial black holes?

I often see it implied that primordial black holes tend to be small compared to stellar masses;

Since primordial black holes did not form from stellar gravitational collapse, their masses can be far below stellar mass (c. 2×10^30 kg)

Primordial Black Holes

Given what we know about the state of the universe at the time of primordial black hole formation, and of the mechanisms by which they formed, what is the average/expected (in a statistical sense) size of such a black hole?

• Since they don't seem to exist, there may not be any way to decide on the parameters of a model that would predict this. – user4552 Oct 2 '19 at 13:53
• @BenCrowell There is no real indication that they don't exist. – mmeent Oct 2 '19 at 14:02

Note that the validity of some of these bounds is subject of ongoing discussion. I'm no expert, so can't vouch for the validity of the particular bounds shown here. Anyway, anything between $$10^{-17}$$ and $$10^2$$ solar masses is still viable as being a some fraction of the total dark matter.