Nibbles & Bits

Announcing Our New IPv6 Subnet Calculator

by | September 1, 2021

We are pleased to announce the initial release of our web-based IPv6 Subnet Calculator! This tool can be used to work within your IP block range and estimate the structure of your IPv6 allocation. Or you can just generate CSV files all day – whatever floats your boat.

The good news is that we actually want to do regular updates to this fun and handy tool. The bad news is that we need your feedback to make those updates happen.

Command-line-based IP calculators have been around for a while, but as networks grow in size and complexity, we may need to think outside the box with the design of our tools and making them accessible when a command line tool isn’t handy.

Other web-based calculators exist, but vary in levels of accessibility. Sipcalc is an example of an existing calculator that has some impressive functionality but is limited to a CLI and has a learning curve for beginners. We wanted to see what we could do with a web-based version and really deliver key elements to be as usable as possible. We know it still needs some work, but we figured we would start with version 1 and see what happens.

Here’s an example of using an existing calculator UI, from, to determine how many addresses are in a given network:

Screengrab of the GestioIP IPv6 subnet calculator. It displays a shortened address of "1234::", a prefix length of "64" with 18.4 quintillion available subnets, plus some additional supporting information. It looks fairly barebones, like an old web form from the 90s.

This tool serves its purpose, but the input for the prefix length is not very intuitive, especially for beginners. The moment you want to do anything more complicated, such as calculating nested subnets, you exceed the limits of this tool.

Now here’s an example using our tool:

Screengrab of the 6Connect IPv6 subnet calculator. It displays a shortened address of "1234::/0", wit a prefix length of "64" entered in a counter field with an output of 18.4 quintillion available subnets, plus some additional supporting information. It has a modern, clean look, with a more interactive UI.

It does not display all the same information yet, but it shows the inputs in an intuitive fashion and displays the most relevant information prominently.

Current benefits over other tools:

  • A more polished graphical user interface
  • CIDR indicators let users know where a bit lands in a v6 address
  • Nest multiple subnets to help you plan your entire network out without leaving the page

Features we are actively developing:

  • Export all possible subnets
    • Exclude ranges of addresses
    • Export as CSV or JSON

Have any ideas on how we could improve this further? Do you use tools like Sipcalc already, and if so, what commands do you frequently use? Feel free to leave any suggestions on GitHub.

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