Subnet Calculator
Compute network, broadcast, host range, wildcard mask and usable host count from any CIDR block. Supports IPv4 and IPv6. Runs entirely in your browser.
About CIDR calculation
CIDR notation (Classless Inter-Domain Routing) describes a range of IPs by a prefix length. 192.168.0.0/24 covers 256 addresses from 192.168.0.0 to 192.168.0.255. This calculator splits the range into network, broadcast, first and last usable host, the wildcard mask and total usable host count. Supports IPv4 and IPv6.
Everything runs in your browser. No request is sent over the network.
Examples
10.0.0.0/8- a full class A private range, 16.7M addresses.192.168.1.64/26- 64 addresses, useful for small subnets.2001:db8::/48- the standard IPv6 allocation for a single site.
Questions
What's a wildcard mask?
The bitwise inverse of the subnet mask. ACLs on Cisco and some firewalls use wildcard notation (0.0.0.255 instead of 255.255.255.0).
Why do /24s have two fewer usable hosts?
IPv4 subnets reserve the network address (all-zero host) and broadcast address (all-one host), so a /24 has 256 addresses but only 254 usable hosts. /31 and /32 are special cases for point-to-point links.
Does IPv6 reserve network and broadcast?
No. IPv6 has no broadcast address and the all-zero address is usable. A /64 has 2^64 usable addresses.
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