CIDR calculator (IPv4 & IPv6)

Client

Enter an IPv4 or IPv6 address with prefix length (for example 192.168.1.0/24 or 2001:db8::/32). Choose the IP version tab, then load an example or paste your own CIDR. All math runs in your browser. To list every child IPv4 subnet of a parent block, use the IPv4 subnet table or the IPv6 address expand & compress for single-address text only.

What this calculates

Given an address and prefix length, the tool derives network, mask, wildcard, broadcast (IPv4), last address, and host counts. It is for planning and documentation—not live routing table lookup.

CIDR input

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IPv4: network and broadcast; usable hosts follow common /31–/32 rules shown below.

Network
192.168.1.0/24
Subnet mask
255.255.255.0
Wildcard mask
0.0.0.255
Broadcast
192.168.1.255
Host addresses
Count: 256192.168.1.1 – 192.168.1.254

Nearby workflows on Toolcore

  • IPv4 subnet table — to enumerate every child prefix inside a parent CIDR block.
  • IPv6 expand & compress — when you need canonical text for a single address without mask math.
  • HTTP headers — to sanity-check Host or forwarded-for values against the range you planned.

Common use cases

  • Plan IPv4 subnets: see network, mask, wildcard, broadcast, and usable hosts for /24 and similar ranges.
  • Validate IPv6 prefix boundaries: network address, last address in range, and address count (including very large subnets).
  • Document firewall or routing rules with a shared CIDR string—copy results locally for runbooks.

Common mistakes to avoid

  • Expecting an IPv6 “broadcast” address

    IPv6 does not use broadcast like IPv4. This tool shows the last address in the subnet range instead.

  • Mixing up /31 and /32 host rules on IPv4

    Point-to-point links often use /31; single-host subnets use /32. Usable host counts follow the conventions shown in the IPv4 tab.

  • Forgetting that prefix length sets the whole boundary

    The network address is the input address with host bits cleared. If your input is not aligned, the computed network may differ from what you typed.

FAQ

How do I switch between IPv4 and IPv6?

Use the IPv4 / IPv6 tabs. If you open the page with a query prefill, values that contain a colon (typical IPv6) select the IPv6 tab automatically.

Does this calculator send my addresses to a server?

No. Parsing and math run entirely in your browser tab.

Why is the IPv6 address count shown as a power of two?

For large subnets the exact integer is enormous; showing 2^n with host-bit count keeps the UI readable while staying accurate.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • ipv4 cidr calculator
  • ipv6 cidr calculator
  • subnet mask to prefix length
  • calculate ip range from cidr

More tools

Related utilities you can open in another tab—mostly client-side.