CIDR / Subnet Calculator
Enter an IP and CIDR prefix (e.g. 192.168.1.0/24) to get the network address, broadcast address, subnet mask and usable host range.
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Invalid IP/CIDR — example: 192.168.1.0/24
CIDR Notation, Broken Down
A CIDR block like 192.168.1.0/24 packs an IP address and a subnet size into one string — the /24 means the first 24 bits are the fixed network portion, leaving 8 bits for host addresses. This tool expands that into every value you actually need: network address, broadcast address, subnet mask, wildcard mask, the first and last usable host, and how many usable hosts the block holds.
Everything is pure binary arithmetic on the 32-bit IPv4 address — no lookup, no external service.
Frequently Asked Questions
Why are the first and last address in a subnet not usable as hosts?
The first address is the network address (identifies the subnet itself) and the last is the broadcast address (sends to every host on the subnet) — neither can be assigned to a single device. The exception is /31 (point-to-point links) and /32 (a single host), where this convention doesn't apply.
What is a wildcard mask?
The bitwise inverse of the subnet mask — used in Cisco ACLs and some routing configs instead of a subnet mask. Where the subnet mask has a 1, the wildcard mask has a 0, and vice versa.
Does this validate that my IP is actually on that network?
No — it treats whatever IP you enter as the base and computes the block from the prefix length. If you want the network address for an arbitrary host IP, that's exactly what the "Network Address" result gives you.
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CIDR / Subnet Calculator