Subnet Calculator (CIDR)
Compute network, broadcast, host range and host count from CIDR. IPv4/IPv6, all in your browser.
What this subnet calculator does
Type a CIDR block (e.g. 192.168.1.0/24 or 2001:db8::/48) and instantly get the network address, broadcast, netmask, wildcard mask, usable host range, host count and total addresses. Everything is computed in your browser, so IPv6 input works even though our server is IPv4-only, and nothing you enter is sent anywhere.
For membership tests, splitting and merging blocks use the CIDR tools. To convert an address between decimal/hex/binary use the IP converter. Background: subnetting and CIDR basics.
Frequently asked questions
Why do /31 and /32 show no usable host range deduction?
For ordinary subnets the network and broadcast addresses are not assigned to hosts, so usable = total − 2. A /31 (RFC 3021 point-to-point link) and a /32 (single host) are special cases where both addresses are usable.
How are IPv6 subnets different here?
IPv6 has no broadcast address and host counts are astronomically large, so the calculator shows the network, the first/last address and the total count rather than a "usable hosts minus two" figure.
Is the calculation done on your server?
No. All math runs locally in JavaScript using BigInt, which is why IPv6 works and why your inputs never leave the browser.