The folks quoting slavery stats might want to check more than one source.
The 1860 census is pretty clear: 8% of the entire US free population owned slaves.
That’s approximately 400k free people owning 4 million enslaved people. That’s a LOT of people in slavery.
13% of the total population of the US was enslaved in 1860.
In 1860 slavery was big in the lower south — only 13 states still practiced slavery and those thirteen states average out to a serious 29% of the free population owning slaves.
South Carolina and Mississippi were especially robust with 46% & 49% of free households owning slaves.