IPv4 / IPv6 subnet calculator
Enter an address with its mask or prefix (192.168.1.10/24, 10.0.0.0 255.255.0.0, 2001:db8::/32): the tool gives the network, host range, mask, wildcard and address count. It also splits a network into subnets, plans a VLSM and checks whether an address belongs to the network.
What the tool does
Every input format
CIDR (192.168.1.10/24), dotted mask (255.255.255.0), wildcard mask (0.0.0.255) or a bare address; IPv4 and IPv6.
Full description
Network, broadcast, first and last usable address, host count, class, type (private, CGNAT, link-local, documentation, ULA…), binary, hexadecimal and reverse DNS name.
Splitting and VLSM
Splits a network into equal subnets, or distributes unequal needs (100, 50, 25 hosts…) from largest to smallest with no overlap.
Edge cases handled
/31 (point-to-point links, RFC 3021), /32 (host), /0, IPv4-mapped addresses, IPv6 compression per RFC 5952.
How to use it
Enter the address with its prefix or mask and submit: the result appears. Then use splitting to divide the network, or VLSM to plan addressing by needs.
FAQ
What is the difference between mask, prefix and wildcard mask?
The prefix (/24) counts network bits; the mask (255.255.255.0) is the same information in dotted notation; the wildcard mask (0.0.0.255) is its inverse, used in access control lists on some devices.
Why two fewer addresses than the total?
In a regular IPv4 network the first address designates the network and the last the broadcast: they are not assigned to hosts. /31 and /32 are exceptions.
What is VLSM?
VLSM (Variable Length Subnet Mask) lets you use subnets of different sizes inside one network, so addresses are not wasted: a large subnet for 100 workstations, a small one for 10 servers.