Here is a quick reference IP numbering chart.
Network Type | Subnet Mask | Number of IP’s |
/ 0 | 0.0.0.0 | 4 billion |
/ 1 | 128.0.0.0 | 2 billion |
/ 2 | 192.0.0.0 | 1billion |
/ 3 | 224.0.0.0 | 500 million |
/ 4 | 240.0.0.0 | 250 million |
/ 5 | 248.0.0.0 | 128 million |
/ 6 | 252.0.0.0 | 64 million |
/ 7 | 254.0.0.0 | 32 million |
/ 8 | 255.0.0.0 | 16 million |
/ 9 | 255.128.0.0 | 8 million |
/ 10 | 255.192.0.0 | 4 million |
/ 11 | 255.224.0.0 | 2 million |
/ 12 | 255.240.0.0 | 1 million |
/ 13 | 255.248.0.0 | 524288 |
/ 14 | 255.252.0.0 | 262144 |
/ 15 | 255.254.0.0 | 131072 |
/ 16 | 255.255.0.0 | 65536 |
/ 17 | 255.255.128.0 | 32768 |
/ 18 | 255.255.192.0 | 16384 |
/ 19 | 255.255.224.0 | 8192 |
/ 20 | 255.255.240.0 | 4096 |
/ 21 | 255.255.248.0 | 2048 |
/ 22 | 255.255.252.0 | 1024 |
/ 23 | 255.255.254.0 | 512 |
/ 24 | 255.255.255.0 | 256 |
/ 25 | 255.255.255.128 | 128 |
/ 26 | 255.255.255.192 | 64 |
/ 27 | 255.255.255.224 | 32 |
/ 28 | 255.255.255.240 | 16 |
/ 29 | 255.255.255.248 | 8 |
/ 30 | 255.255.255.252 | 4 |
/ 31 | 255.255.255.254 | 2 |
/ 32 | 255.255.255.255 | 1 |
The first few on the list would be very difficult to manage network and the last two meaningless subnet mask which would serve no purpose since the only two ip addresses available are taken by the network number and broadcast address.