CIDR subnet calculator (IPv4 and IPv6)
IPv4/IPv6 subnet calculator. Paste a CIDR, get everything you need.
About this tool
Paste an IPv4 or IPv6 CIDR block and get the network and broadcast addresses, the first and last usable host, the netmask and wildcard, and the address count. It works out the bit arithmetic so you don't have to do it in your head during a change window.
Good for
- Checking what a /27 actually covers before you write the firewall rule or security group
- Sanity-checking a subnet plan, or reading an unfamiliar IPv6 prefix
- Getting the wildcard mask for ACL syntax that wants it inverted
Not for
- IP address management: it doesn't track allocations or spot overlaps between VPCs and accounts
- Telling you whether an address is in use, or reachable