A numerical definition of what central banks consider as price stability based on a specific price index is about 2 percent in terms of the year-on-year rate of change in the CPI; this has become the global standard in recent years.
While I will not go into detail due to time constraints, this figure – 2 percent – takes into account the upward bias in the CPI, that is, the tendency of the index to overstate inflation, and provides a buffer allowing to sufficiently lower real interest rates should the economy deteriorate.