IP Block Notation Conventions

Allocation Size Number of /24s Number of Host
Addresses
/32  <1 1
/31  <1 2
/30 <1 4
/29 <1 8
/28 <1 16
/27 <1 32
/26 <1 64
/25 <1 128
/24 1 256
/23 2 512
/22 4 1,024
/21 8 2,048
/20 16 4,096
/19 32 8,192
/18 64 16,384
/17 128 32,768
/16 256 65,536
/15 512 131,072
/14 1,024 262,144
/13 2,048 524,288
/12 4,096 1,048,576
/11 8,192 2,097,152
/10 16,384 4,194,304
/9 32,768 8,388,608
/8 65,536 16,777,216

 


Subnet Mask Number
255.255.255.x
Increment
(i.e. IP number)
255 1
254 2
252 4
248 8
240 16
224 32
192 64
128 128


IANA IPv4 Address Space Registry