Subnet Calculator
Enter a network in CIDR notation to see the subnet breakdown.
What is CIDR notation?
CIDR notation pairs an IPv4 address with a prefix length: 192.168.1.0/24 means the first 24 bits are the network and the remaining 8 bits address 256 hosts (.0–.255). A plain address without /prefix is rejected — add the prefix so the tool never guesses.
Why are network and broadcast excluded?
The network address identifies the subnet and the broadcast address reaches every host in it — neither is assignable to a device. The usable range runs from network + 1 to broadcast − 1. Two edge cases break this math: a /32 is a single host, and a /31 is a point-to-point link (RFC 3021) where both addresses belong to the two endpoints.
Is my data safe?
Yes. Subnet math is plain integer arithmetic that runs locally in your browser. No data ever leaves your device.