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Technology

IP Address Range Calculator

Address counts across prefixes.

Enter your values

Enter the parent prefix you are working with.

Enter the child prefix you are working with.

Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.

Results
Subnets available
256
Addresses in parent
65,536
Addresses per child
256
Usable hosts per child
254

Quick answer

Each bit added to a prefix halves the number of addresses in the block.

Addresses = 2^(32 − prefix)

At a glance

What it doesAddress counts across prefixes.
CategoryTechnology
Inputs neededParent prefix, Child prefix
Main outputSubnets available
FormulaAddresses = 2^(32 − prefix)
CostFree — no sign-up, no download

How to use the IP Address Range Calculator

  1. 1Enter the parent prefix you own.
  2. 2Enter the child prefix you want to carve out.
  3. 3Read how many subnets you get.

Inputs explained

Parent prefix
Enter the parent prefix you are working with.
Child prefix
Enter the child prefix you are working with.

Worked example

Using the values the calculator loads with:

Inputs

  • Parent prefix16
  • Child prefix24

Results

  • Subnets available256
  • Addresses in parent65,536
  • Addresses per child256
  • Usable hosts per child254

Frequently asked questions

How many /24s in a /16?

256.

Does IPv6 work the same?

The maths is identical but with 128 bits instead of 32.

What do I need to enter into the IP Address Range Calculator?

Just 2 values: parent prefix, child prefix. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.

How does the IP Address Range Calculator work out the answer?

Each bit added to a prefix halves the number of addresses in the block. It applies the formula Addresses = 2^(32 − prefix) and shows the working so you can check each step by hand.

Is the IP Address Range Calculator free, and do I need an account?

It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.

Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.