Subnet Calculator
An IPv4 address and a prefix, or one CIDR. Network, broadcast, first host, last host and usable host count.
Frequently asked questions
Does this do IPv6?
No. IPv4 only. A /31 shows both addresses as usable. A /32 is a single host.
Can I type the prefix in its own field?
Yes. Use a CIDR in the address, or an address plus a prefix, not both at once.