IPv4 Subnet & CIDR Calculator

Network, broadcast, mask, wildcard, host range & count from any CIDR.

Network, broadcast, mask, wildcard, host range & count from any CIDR. Free and 100% private — runs entirely in your browser, nothing is ever uploaded.

About IPv4 Subnet & CIDR Calculator

The IPv4 Subnet & CIDR Calculator is a free, in-browser tool that turns a CIDR block like 192.168.1.0/24 into its full network breakdown: network and broadcast addresses, netmask, Cisco wildcard mask, first and last usable host, usable and total host counts, address class, and whether the range is private (RFC 1918) or public. Use it whenever you need to plan a subnet, double-check a firewall or ACL rule, or expand a block into a list of every address. All subnet math runs locally with plain bit-arithmetic, so nothing you type is ever uploaded.

How to use IPv4 Subnet & CIDR Calculator

  1. Type an address in the IP / CIDR field, such as 192.168.1.0/24, a bare IP like 10.0.0.5 (treated as /32), or an explicit netmask form like 10.0.0.0/255.255.255.0.
  2. Read the network details grid: network, broadcast, normalised CIDR, netmask, wildcard, prefix, first and last host, usable hosts, total addresses, class, and private/public scope.
  3. Click a common-prefix chip (/8, /16, /24, /30) to re-mask the same address instantly, or pick one of the example chips to load a sample block.
  4. Use the Copy a field panel to copy any single value, or the host range, to your clipboard for pasting into configs or tickets.
  5. Click List all addresses to expand the block into every IP it contains (capped at 65,536 for responsiveness), then Copy all to grab the whole list.
  6. Share your result by copying the page URL: the CIDR is stored in the link, so a colleague opening it sees the same calculation.

Frequently asked questions

What input formats does the subnet calculator accept?
Three forms: a CIDR block (192.168.1.10/24), a bare IP address with no prefix (which defaults to /32), or an IP with an explicit dotted netmask (10.0.0.0/255.0.0.0). Invalid octets or non-contiguous masks are flagged with a clear error message.
How are /31 and /32 blocks handled?
A /32 is a single host, so first host, last host and network are all the same address and the usable count is 1. A /31 follows RFC 3021 for point-to-point links: both addresses are counted as usable, with no network or broadcast reserved, giving 2 usable hosts.
What is the difference between the netmask and the wildcard mask?
The netmask (for example 255.255.255.0) marks the network bits, while the wildcard mask is its bit-inverse (0.0.0.255) and is the format Cisco ACLs and OSPF expect. The tool shows both so you can copy whichever your config needs.
Can I get a list of every IP address in a block?
Yes. Click List all addresses to expand the CIDR into every address it contains, then use Copy all. Very large blocks are capped at 65,536 addresses shown so the page stays responsive, and a banner tells you when the list was truncated.
Is my IP data uploaded or logged anywhere?
No. Every calculation is plain bit-arithmetic that runs entirely in your browser. Nothing you enter is sent to a server, stored, or logged, which makes it safe to use with internal or production network addressing.
How do I share a subnet result with a teammate?
The CIDR you enter is written into the page URL, so just copy the address bar and send it. When your teammate opens the link, the calculator loads with the same block already computed.