For the subnetwork calculation, simply enter the IP-address in the form, select the desired bit mask (or prefix length for IPv6) and click "Calculate". This calculator works totally well with IPv4 and IPv6 protocols.
When entering an IPv4 address it can be partially abstract. For example, if you want to make the calculations for the subnet 10.2/16, then allowed to enter instead of full address (10.2.0.0) only part of it (10.2). IPv6-addresses must be entered fully, only standard zero-compression is allowed.