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IPv4 Subnet & CIDR Calculator

Calculate IPv4 networks, masks, ranges, address types, and child subnets locally.
Local browser processing
Addresses and calculation inputs stay in this browser. They are not uploaded, resolved, scanned, or sent to analytics.
Address or network
Subnet mask when CIDR is omitted
Child prefix to preview
Result
Enter values and run the tool to see the local result.

Standards and authoritative references

  • RFC 4632 — Classless Inter-domain Routing
  • RFC 3021 — 31-Bit Prefixes on IPv4 Point-to-Point Links

What this tool does

Enter an IPv4 address with a CIDR prefix to calculate its network, broadcast, masks, address count, host range, address type, integer and hexadecimal forms, and child subnets.

How to use it

  1. Paste or enter the content you want to process.
  2. Choose a mode and run the tool.
  3. Review the result and limitations, then copy what you need.

Limitations

This release supports IPv4 only. /31 and /32 are labeled explicitly, and no network reachability or address ownership check is performed.

Related tools

IPv6 Subnet CalculatorIP Range to CIDR Converter

Frequently asked questions

What does CIDR mean?
The prefix length states how many leading address bits identify the network.
How are /31 networks handled?
Both addresses are counted for point-to-point use under RFC 3021.
Does this support IPv6?
No. This page calculates IPv4 subnets only.
Does it contact the network?
No. All calculations are pure local arithmetic.