For number of addresses, I always used this formula:
32 – (cidr) = X
then 2^x = number of addresses
To get the number of hosts, subtract with 2 (network and subnet mask)
Example: (to get # of addresses and hosts of /24)
32 – 24 = 8
2^8 = 256 (total number of addresses)
256 -2 = 254 (total number of hosts)
| CIDR | Addresses | Netmask | Wildcard |
| /32 | 1 | 255.255.255.255 | 0.0.0.0 |
| /31 | 2 | 255.255.255.254 | 0.0.0.1 |
| /30 | 4 | 255.255.255.252 | 0.0.0.3 |
| /29 | 8 | 255.255.255.248 | 0.0.0.7 |
| /28 | 16 | 255.255.255.240 | 0.0.0.15 |
| /27 | 32 | 255.255.255.224 | 0.0.0.31 |
| /26 | 64 | 255.255.255.192 | 0.0.0.63 |
| /25 | 128 | 255.255.255.128 | 0.0.0.127 |
| /24 | 256 | 255.255.255.0 | 0.0.0.255 |
| /23 | 512 | 255.255.254.0 | 0.0.1.255 |
| /22 | 1,024 | 255.255.252.0 | 0.0.3.255 |
| /21 | 2,048 | 255.255.248.0 | 0.0.7.255 |
| /20 | 4,096 | 255.255.240.0 | 0.0.15.255 |
| /19 | 8,192 | 255.255.224.0 | 0.0.31.255 |
| /18 | 16,384 | 255.255.192.0 | 0.0.63.255 |
| /17 | 32,768 | 255.255.128.0 | 0.0.127.255 |
| /16 | 65,536 | 255.255.0.0 | 0.0.255.255 |
| /15 | 131,072 | 255.254.0.0 | 0.1.255.255 |
| /14 | 262,144 | 255.252.0.0 | 0.3.255.255 |
| /13 | 524,288 | 255.248.0.0 | 0.7.255.255 |
| /12 | 1,048,576 | 255.240.0.0 | 0.15.255.255 |
| /11 | 2,097,152 | 255.224.0.0 | 0.31.255.255 |
| /10 | 4,194,304 | 255.192.0.0 | 0.63.255.255 |
| /9 | 8,388,608 | 255.128.0.0 | 0.127.255.255 |
| /8 | 16,777,216 | 255.0.0.0 | 0.255.255.255 |
| /7 | 33,554,432 | 254.0.0.0 | 1.255.255.255 |
| /6 | 67,108,864 | 252.0.0.0 | 3.255.255.255 |
| /5 | 134,217,728 | 248.0.0.0 | 7.255.255.255 |
| /4 | 268,435,456 | 240.0.0.0 | 15.255.255.255 |
| /3 | 536,870,912 | 224.0.0.0 | 31.255.255.255 |
| /2 | 1,073,741,824 | 192.0.0.0 | 63.255.255.255 |
| /1 | 2,147,483,648 | 128.0.0.0 | 127.255.255.255 |
| /0 | 4,294,967,296 | 0.0.0.0 | 255.255.255.255 |
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