Subnet Calculator
IPv4 CIDR mask, hosts, broadcast, first / last
About Subnet Calculator
What this tool does
A classic IPv4 CIDR calculator. Enter an IP in CIDR notation (e.g. 10.0.0.0/22) and get the network address, subnet mask, wildcard mask, broadcast address, first and last usable host, total addresses, usable host count, and class (A/B/C).
When to use it
- Sizing a new VLAN or VPC subnet
- Verifying a firewall rule covers the intended host range
- Teaching CIDR / subnetting in a networking class
- Sanity-checking a route table before applying it
Frequently asked questions
IPv4 only for now. IPv6 subnet math is on the roadmap.
The tool reports 2 / 1 total addresses respectively with 0 usable hosts and no broadcast — the correct RFC-3021 answer for point-to-point links.
You can — it defaults to /32 (single host).
No. Subnet math runs entirely in your browser.
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Subnet Calculator
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