IP Subnet Calculator

Free, fast IPv4 and IPv6 subnetting for network engineers — with a subnet splitter, multi-vendor config generation, and a world clock for coordinating work across time zones. No ads, no clutter, no page reloads.

Network Address
Broadcast Address
Subnet Mask
Wildcard Mask
First Usable Host
Last Usable Host
Usable Hosts
IP Class / Type
Compressed
Expanded
Prefix
Scope / Type
Network Address
Last Address in Range
Total Addresses
Subnet Splitter
Copied

Everything in the toolkit

Four tools, one tab. No sign-up, no ads, no page reloads.

v4 / v6
Subnet Calculator

Network, broadcast, mask, wildcard, and usable host range — instantly, for any prefix.

/ split
Subnet Splitter

Divide any network into equal subnets for VLAN and site planning, IPv4 or IPv6.

cfg
Config Generator

Pasteable ACLs, prefix lists, static routes, and address objects for Juniper, Cisco IOS-XE, Arista EOS, and Palo Alto.

tz
World Clock

Every team city on one aligned timeline, with drag-to-select windows and full IANA time zone support.

What Subnet Wizard Does

Subnet Wizard is a free IPv4 and IPv6 subnet calculator built for network engineers who need fast, accurate answers without wading through ads or clunky legacy tools. Enter an IP address and a prefix length (or subnet mask), and it instantly works out the network address, broadcast address, usable host range, and total host count for that subnet — all computed client-side against Python's standard ipaddress library, so the math holds up the same way it would in a script or a router's own CLI.

Understanding the Results

A few of the fields are worth a quick explanation if you don't touch them daily. The network address identifies the subnet itself — the "zero" address of the range. The broadcast address is the highest address in an IPv4 subnet, reserved for broadcasting to every host on that segment. The wildcard mask is the inverse of the subnet mask, used in access control lists (ACLs) on platforms like Cisco IOS and Arista EOS, where matching logic is expressed as "don't care" bits rather than a standard mask. The usable host range excludes the network and broadcast addresses, giving you the actual assignable IPs for that subnet.

Beyond the Basic Calculator

The Subnet Splitter divides a network into a chosen number of equally sized subnets in one pass — useful for planning VLANs or allocating address space across sites without working out the prefix math by hand. The Config Generator takes the network details you've already worked out and turns them into real, platform-correct syntax for Juniper, Cisco IOS-XE, Arista EOS, and Palo Alto — ACLs, prefix lists, static routes, and address objects — so you can go from planning straight to a pasteable config. And since coordinating maintenance windows and calls across a distributed team is its own kind of headache, the World Clock lays out every added city on one aligned timeline, with drag-to-select time ranges and full IANA time zone support, so you can find a workable window without doing the math in your head.

About Us

Subnet Wizard is built in Austin, Texas by network engineers with two decades of experience designing and troubleshooting large-scale networks for some of the biggest companies in the world. We built the tool we always wished existed: fast, accurate, and free of the ads and clutter that weigh down the older calculator sites — something you can keep open in a tab all day and trust in the middle of a change window.

Accuracy matters more than anything else in this line of work, so every calculation runs on the same foundations used in production tooling — Python's standard ipaddress library for subnet math and the IANA time zone database for the world clock — meaning the results here match what your routers, scripts, and schedulers will tell you. Everything on the site is developed in-house, and it's free to use. If Subnet Wizard saves you time, feel free to link to it from your own docs, runbooks, or team wikis.

Contact Us

Found a bug, have a feature idea, or just want to say hi? Send us a note — if it's about a calculation, include the inputs you used so we can reproduce it.

We'll never sell your email or data — it's used only to reply to you.