In the Mandalorian, it is stated that the entirety of the planet of mandalore was destroyed in the great purge, but some Mandalorians (both the civilians and the Mandalorian warriors) survived.
After the night of a thousand tears, I believe that most to all of the Mandalorians on Mandalore were destroyed, along with potentially even civillians, but this doesn't include the other planets.
For example, Concord Dawn, Kalevala, Krownest, and Concordia all housed Mandalorian coverts, along with civilians - the show speaks of many unknown hidden coverts, probably with the survivors of different clans.
Mandalorians were probably also present as bounty hunters, mercenaries, or travellers.
In my opinion, about 20-30% of Mandalorians may have survived, with perhaps a larger percentage of civilian survivors
What do you think?