Your simple subnet cheat sheet and subnet calculator

About Us is a simple subnetting cheat sheet website, with a great little subnet calculator integrated. We're always aiming to keep the website clean, fast and useful for everyone to use with ease.

The tool will take an entered IP address and netmask (provided in slash notation), it will then calculate the subnet that this address resides within and display the resulting network and broadcast addresses, along with the usable hosts, all of this is shown in normal human readable format but also binary format.

IT system engineers and especially network administrators will find themselves performing subnetting tasks on a daily basis, this tool aims to speed up the process of doing this by hand or mentally, and also increase the accuracy, a number of features also exist to automatically show usable ACL rules based on the subnet entered, for example Cisco IP standard or extended ACL's along with IPTables examples.

We’ve found that many of the subletting web based tools out there are just so clunky to use, too many drop downs and hard to visually see what’s going on, this website improves on the norm and we’re also planning on providing a number of cool blog posts on how to understand subletting better!

If you like what you see, please don’t forget to spread the word :)

Also here's some example pages:

The typical -
A Google Subnet -
Load of Private -
Level 3 DNS -

You can also see things like RFC1918 - This defines private IP's, they are: