IP Subnet Calculator (IPv4 & IPv6)

IPv4 and IPv6 network details: network address, broadcast, usable host range, subnet mask, wildcard mask, CIDR notation, and binary representation.

Yes. Enter any IPv6 address (with or without :: compression) and a prefix length 0-128 — the tool shows expanded address, network, first/last address, and total count computed with BigInt for 128-bit precision.

Yes. After calculating an IPv4 network, specify a longer target prefix (e.g. /24 into /26) and the tool lists the first 10 resulting subnets.

Yes, the IP Subnet Calculator (IPv4 & IPv6) is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The IP Subnet Calculator (IPv4 & IPv6) processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the IP Subnet Calculator (IPv4 & IPv6) is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the IP Subnet Calculator (IPv4 & IPv6) in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The IP Subnet Calculator (IPv4 & IPv6) works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

A subnet's total addresses equal 2 raised to the number of host bits, which is 32 minus the prefix length. A normal subnet then reserves two of those for the network and broadcast addresses, leaving the usable host count. A /24 has 8 host bits, so 256 total addresses and 254 usable; a /25 has 128 total and 126 usable; a /26 has 64 total and 62 usable. Each step of one in the prefix roughly halves the block. The pattern continues: /27 gives 30 usable, /28 gives 14, and /29 gives 6. The point-to-point /31 and host /32 prefixes are special cases handled separately. Rather than memorize the table, enter any address and prefix in the calculator above to see the exact total and usable host counts instantly.

A subnet mask and a wildcard mask are bit-for-bit inverses of each other. The subnet mask marks network bits with 1s and host bits with 0s, so a /24 mask is 255.255.255.0. The wildcard mask flips every bit, making the same /24 read 0.0.0.255, where 1s now mark the bits that are allowed to vary. Subnet masks describe how a network is divided, while wildcard masks are used in access control lists and routing statements on Cisco IOS, where you specify which address bits to match and which to ignore. They always sum to 255 in each octet. The calculator above shows both masks in dotted-decimal for any prefix you enter, so you can copy the wildcard straight into a firewall or ACL rule without converting by hand.

Standard subnets reserve the first address as the network identifier and the last as the broadcast address, so a /29 with 8 total addresses leaves only 6 usable for hosts. A /31, however, has just 2 total addresses, and reserving both would leave none usable. RFC 3021 solved this for point-to-point links: on a /31 both addresses are assignable to the two router interfaces, giving 2 usable hosts and conserving scarce IPv4 space. A /32 is a single-host route used for loopbacks and individual host entries, so it counts as 1 usable address with no network or broadcast reservation. The calculator above applies these RFC 3021 edge cases automatically, reporting 2 usable for a /31 and 1 for a /32 instead of the misleading zero a naive formula would produce.

Private addresses come from the ranges RFC 1918 reserves for internal networks: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Any address inside those blocks is private and is not routable on the public internet, so it must be translated through NAT to reach external sites. Everything outside those ranges that is also outside the special-use blocks is public. The calculator also flags other special types: 127.0.0.0/8 is loopback, 169.254.0.0/16 is link-local (APIPA, assigned when DHCP fails), 224.0.0.0 through 239.255.255.255 is multicast, and the highest ranges are reserved or experimental. It even reports the legacy class A through E. Enter any IPv4 address above and the tool labels it as Public, Private, Loopback, Link-local, Multicast, or Reserved at a glance.

The slash number in CIDR notation is the prefix length: the count of leading bits, out of 32 for IPv4, that belong to the network portion of the address. A /24 means the first 24 bits identify the network and the remaining 8 bits identify hosts, which is why a /24 holds 256 addresses. CIDR replaced the old class system, letting you size a network to any prefix from /0 to /32 instead of being locked to fixed class A, B, or C boundaries. A larger slash number means a smaller network with fewer hosts; a smaller number means a bigger block. The binary view in the calculator above lines up the address and mask bit by bit, making it easy to see exactly which bits the prefix claims for the network and which are left for hosts.