This cidr calculator takes the figures you already have and applies the relationship behind cidr calculations for you, giving cidr subnet width, cidr wildcard 1 and cidr wildcard 2 from subnet mask width, first octet, second octet, third octet, fourth octet, first octet of ip, second octet of ip, third octet of ip, fourth octet of ip, first octet, second octet, third octet, fourth octet, if else and one way.
What Is the CIDR Calculator?
The cidr calculator turns subnet mask width, first octet, second octet, third octet, fourth octet, first octet of ip, second octet of ip, third octet of ip, fourth octet of ip, first octet, second octet, third octet, fourth octet, if else and one way into cidr subnet width, cidr wildcard 1 and cidr wildcard 2.
It is a quick way to get from the numbers you have to the number you need, without setting up a spreadsheet or reaching for a formula.
How the CIDR Works
Each result follows from the ones before it, and the calculator shows every step, so a surprising answer can be traced back to the input that caused it.
Round your inputs to the precision you actually know, and keep more precision than that in the intermediate steps.
Getting a Result You Can Trust
Run the calculation twice with slightly different inputs. A sensible calculator moves its output in proportion; a wild change points to a unit or a decimal point problem in what you entered.
Write the inputs down next to the answer. It takes a moment and it is the difference between a number you can explain and one you cannot.
A Worked Example
Working through an example, with subnet mask width set to 10, first octet set to 5, second octet set to 2, the calculator returns subnet1 of 255, and subnet2 of 192, and subnet3 of 0. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out cidr subnet width?
Enter subnet mask width, first octet, second octet, third octet, fourth octet, first octet of ip, second octet of ip, third octet of ip, fourth octet of ip, first octet, second octet, third octet, fourth octet, if else and one way. The calculator then works through the relationship and reports cidr subnet width, cidr wildcard 1 and cidr wildcard 2.
What does the cidr actually calculate?
It takes subnet mask width, first octet, second octet, third octet, fourth octet, first octet of ip, second octet of ip, third octet of ip, fourth octet of ip, first octet, second octet, third octet, fourth octet, if else and one way and converts them into cidr subnet width, cidr wildcard 1 and cidr wildcard 2 using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter subnet mask width?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Do I have to fill in every field?
Only the fields a particular result depends on. If you leave one blank, the results that need it simply show a note instead of a number, and everything else still works.
Does anything you type get stored?
No. The whole calculation runs inside your browser, and nothing you enter is uploaded, logged or sent anywhere.