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IPv4 / IPv6 Subnet & CIDR Calculator

Enter an address in CIDR notation. IPv4 and IPv6 are both supported and detected automatically. Everything is computed locally in your browser.

📖 Guide: CIDR & subnetting explained

Last updated: September 9, 2026

How to use this tool

1. Enter an address in CIDR notation, for example 192.168.1.0/24 or 2001:db8::/32, and click Calculate.
2. IPv4 results show the network and broadcast address, usable host range, and subnet mask.
3. IPv6 results show the network range and address count, since IPv6 has no broadcast address.

Use it when planning a new subnet, checking whether two ranges overlap, or figuring out how many usable addresses a given prefix length actually leaves you — arithmetic that's easy to get wrong by hand once you're past a /24.

Sample output

Entering 192.168.1.0/24 returns:

The same address as a /25 instead would give you two smaller subnets of 126 usable hosts each — a good example of why the prefix length matters as much as the address itself.