ipcalc

#ipcalc 172.121.0.0/22
Address:   172.121.0.0          10101100.01111001.000000 00.00000000
Netmask:   255.255.252.0 = 22   11111111.11111111.111111 00.00000000
Wildcard:  0.0.3.255            00000000.00000000.000000 11.11111111
=>
Network:   172.121.0.0/22       10101100.01111001.000000 00.00000000
HostMin:   172.121.0.1          10101100.01111001.000000 00.00000001
HostMax:   172.121.3.254        10101100.01111001.000000 11.11111110
Broadcast: 172.121.3.255        10101100.01111001.000000 11.11111111
Hosts/Net: 1022                  Class B

Here is a table of network masks:

Here is a table of network masks:

Short   Full                    Maximum         Comment
Form    Form                    #Machines

/8      /255.0.0.0              16,777,215      Used to be called an `A-class'
/16     /255.255.0.0            65,535          Used to be called an `B-class'
/17     /255.255.128.0          32,767
/18     /255.255.192.0          16,383
/19     /255.255.224.0          8,191
/20     /255.255.240.0          4,095
/21     /255.255.248.0          2,047
/22     /255.255.252.0          1,023
/23     /255.255.254.0          511
/24     /255.255.255.0          255             Used to be called a `C-class'
/25     /255.255.255.128        127
/26     /255.255.255.192        63
/27     /255.255.255.224        31
/28     /255.255.255.240        15
/29     /255.255.255.248        7
/30     /255.255.255.252        3