Private IPv4 ranges

Range from 10.0.0.0 to 10.255.255.255 
10.0.0.0 network with 255.0.0.0 or /8 (an 8-bit) mask

Range from 172.16.0.0 to 172.31.255.255 
172.16.0.0 network with 255.240.0.0 or /12 (an 12-bit) mask

A 192.168.0.0 to 192.168.255.255 range,
192.168.0.0 network with 255.255.0.0 or /16 (an 16-bit) mask

255.0.0.0 = /8      = 11111111.00000000.00000000.00000000
255.255.0.0 = /16   = 11111111.11111111.00000000.00000000
255.255.255.0 = /24 = 11111111.11111111.11111111.00000000