$ ipcalc 128.235.0.0/16 -s 5000 5000
Address:   128.235.0.0          10000000.11101011. 00000000.00000000
Netmask:   255.255.0.0 = 16     11111111.11111111. 00000000.00000000
Wildcard:  0.0.255.255          00000000.00000000. 11111111.11111111
=>
Network:   128.235.0.0/16       10000000.11101011. 00000000.00000000
HostMin:   128.235.0.1          10000000.11101011. 00000000.00000001
HostMax:   128.235.255.254      10000000.11101011. 11111111.11111110
Broadcast: 128.235.255.255      10000000.11101011. 11111111.11111111
Hosts/Net: 65534                 Class B

1. Requested size: 5000 hosts
Netmask:   255.255.224.0 = 19   11111111.11111111.111 00000.00000000
Network:   128.235.0.0/19       10000000.11101011.000 00000.00000000
HostMin:   128.235.0.1          10000000.11101011.000 00000.00000001
HostMax:   128.235.31.254       10000000.11101011.000 11111.11111110
Broadcast: 128.235.31.255       10000000.11101011.000 11111.11111111
Hosts/Net: 8190                  Class B

2. Requested size: 5000 hosts
Netmask:   255.255.224.0 = 19   11111111.11111111.111 00000.00000000
Network:   128.235.32.0/19      10000000.11101011.001 00000.00000000
HostMin:   128.235.32.1         10000000.11101011.001 00000.00000001
HostMax:   128.235.63.254       10000000.11101011.001 11111.11111110
Broadcast: 128.235.63.255       10000000.11101011.001 11111.11111111
Hosts/Net: 8190                  Class B

Needed size:  16384 addresses.
Used network: 128.235.0.0/18
Unused:
128.235.64.0/18
128.235.128.0/17