According to standards set forth in Internet Engineering Task Force (IETF) document RFC-1918, the following IPv4 address ranges have been reserved by the IANA for private internets, and are not publicly routable on the global internet:

10.0.0.0/8 IP addresses: 10.0.0.0 — 10.255.255.255
172.16.0.0/12 IP addresses: 172.16.0.0 — 172.31.255.255
192.168.0.0/16 IP addresses: 192.168.0.0 – 192.168.255.255

Note that only a portion of the “172” and the “192” address ranges are designated for private use.

ref: ARIN