| bit | netmask | Cisco mask | hosts | usable hosts | Class |
| /4 | 240.0.0.0 | 15.255.255.255 | 268435456 | 268435454 | |
| /5 | 248.0.0.0 | 7.255.255.255 | 134217728 | 134217726 | |
| /6 | 252.0.0.0 | 3.255.255.255 | 67108864 | 67108862 | |
| /7 | 254.0.0.0 | 1.255.255.255 | 33554432 | 33554430 | |
| /8 | 255.0.0.0 | 0.255.255.255 | 16777216 | 16777214 | A Class |
| /9 | 255.128.0.0 | 0.127.255.255 | 8388608 | 8388606 | |
| /10 | 255.192.0.0 | 0.63.255.255 | 4194304 | 4194302 | |
| /11 | 255.224.0.0 | 0.31.255.255 | 2097152 | 2097150 | |
| /12 | 255.240.0.0 | 0.15.255.255 | 1048576 | 1048574 | |
| /13 | 255.248.0.0 | 0.7.255.255 | 524288 | 524286 | |
| /14 | 255.252.0.0 | 0.3.255.255 | 262144 | 262142 | |
| /15 | 255.254.0.0 | 0.1.255.255 | 131072 | 131070 | |
| /16 | 255.255.0.0 | 0.0.255.255 | 65536 | 65534 | B Class |
| /17 | 255.255.128.0 | 0.0.127.255 | 32768 | 32766 | |
| /18 | 255.255.192.0 | 0.0.63.255 | 16384 | 16382 | |
| /19 | 255.255.224.0 | 0.0.31.255 | 8192 | 8190 | |
| /20 | 255.255.240.0 | 0.0.15.255 | 4096 | 4094 | |
| /21 | 255.255.248.0 | 0.0.7.255 | 2048 | 2046 | |
| /22 | 255.255.252.0 | 0.0.3.255 | 1024 | 1022 | |
| /23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 | |
| /24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 | C Class |
| /25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 | |
| /26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 | |
| /27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 | |
| /28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 | |
| /29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 | |
| /30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 | |
| /31 | point to point links only | ||||
| /32 | 255.255.255.255 | use host notaition | 1 | 1 | |