The following table translates the traditional netmask format to its CIDR notation. Additionally you can see how many addresses can exist in a subnet with a certain netmask.
| Netmask | CIDR | Nr of IPs |
|---|---|---|
| 255.255.255.255 | 32 | 1 |
| 255.255.255.254 | 31 | 2 |
| 255.255.255.252 | 30 | 4 |
| 255.255.255.248 | 29 | 8 |
| 255.255.255.240 | 28 | 16 |
| 255.255.255.224 | 27 | 32 |
| 255.255.255.192 | 26 | 64 |
| 255.255.255.128 | 25 | 128 |
| 255.255.255.0 | 24 | 256 |
| 255.255.254.0 | 23 | 512 |
| 255.255.252.0 | 22 | 1.024 |
| 255.255.248.0 | 21 | 2.048 |
| 255.255.240.0 | 20 | 4.096 |
| 255.255.224.0 | 19 | 8.192 |
| 255.255.192.0 | 18 | 16.384 |
| 255.255.128.0 | 17 | 32.768 |
| 255.255.0.0 | 16 | 65.536 |
| 255.254.0.0 | 15 | 131.072 |
| 255.252.0.0 | 14 | 262.144 |
| 255.248.0.0 | 13 | 524.288 |
| 255.240.0.0 | 12 | 1.048.576 |
| 255.224.0.0 | 11 | 2.097.152 |
| 255.192.0.0 | 10 | 4.194.304 |
| 255.128.0.0 | 9 | 8.388.608 |
| 255.0.0.0 | 8 | 16.777.216 |
| 254.0.0.0 | 7 | 33.554.432 |
| 252.0.0.0 | 6 | 67.108.864 |
| 248.0.0.0 | 5 | 134.217.728 |
| 240.0.0.0 | 4 | 268.435.456 |
| 224.0.0.0 | 3 | 536.870.912 |
| 192.0.0.0 | 2 | 1.073.741.824 |
| 128.0.0.0 | 1 | 2.147.483.648 |
| 0.0.0.0 | 0 | 4.294.967.296 |