Example: 192.168.220.0/24

CIDR Cheat Sheet
Notation Netmask # of IP Addresses
/32 255.255.255.255 1
/31 255.255.255.254 2
/30 255.255.255.252 4
/29 255.255.255.248 8
/28 255.255.255.240 16
/27 255.255.255.224 32
/26 255.255.255.192 64
/25 255.255.255.128 128
/24 255.255.255.0 256
/23 255.255.254.0 256*2
/22 255.255.252.0 256*4
/21 255.255.248.0 256*8
/20 255.255.240.0 256*16
/19 255.255.224.0 256*32
/18 255.255.192.0 256*64
/17 255.255.128.0 256*128
/16 255.255.0.0 65536
/15 255.254.0.0 65536*2
/14 255.252.0.0 65536*4
/13 255.248.0.0 65536*8
/12 255.240.0.0 65536*16
/11 255.224.0.0 65536*32
/10 255.192.0.0 65536*64
/9 255.128.0.0 65536*128
/8 255.0.0.0 16777216
/7 254.0.0.0 16777216*2
/6 252.0.0.0 16777216*4
/5 248.0.0.0 16777216*8
/4 240.0.0.0 16777216*16
/3 224.0.0.0 16777216*32
/2 192.0.0.0 16777216*64
/1 128.0.0.0 16777216*128
/0 0.0.0.0 4294967295