Subnet Calculator
Quick answer
Enter IP and prefix—see network address, broadcast, first/last host, and host count.
For a related estimate, see Bandwidth Calculator.
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Off-by-one
Usable hosts exclude network and broadcast on traditional IPv4 networks—/31 and /32 behave differently (point-to-point RFC).
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CIDR combines an address with a prefix length to describe a block; hosts = 2^(32-prefix) minus reserved addresses on IPv4. Use it when you are splitting VPCs, writing firewall rules, or planning office LANs. See also DNS lookup for a related utility in this cluster.
How to use this calculator
- Open the tool: Enter base IPv4 and CIDR (e.g., /24).
- Tune inputs: Read network/broadcast automatically.
- Read the output: Carve child subnets if the tool supports split views.
Real-world examples
- 192.168.1.0/24: 254 usable hosts in classic classful thinking—verify device constraints.
- /28 carve: Only 14 usable hosts—plan for gateway IP reservation.
Tips & gotchas
Document reserved ranges for routers, load balancers, and DHCP pools—future you will thank you.
FAQ
IPv6?
Address space math differs—use IPv6-specific tools for prefix planning.
Does this tool send my text to a server?
Calciverse runs in your browser; we do not store your inputs on our servers for these utilities. Anything that uses network APIs (for example DNS lookup) only sends what you explicitly request.
Why do results differ from another site?
Rounding, defaults, and implementation details (color spaces, tokenizers, DNS resolvers) can differ. Compare definitions, not just the headline number.