IPv4 Subnet Mask & CIDR Calculator

Calculate usable host IP count, wildcards, and netmask octets from CIDR prefix length (/0 to /32).

  • 100% free
  • Private in browser
  • No signup
  • No watermarks
Total IP Addresses
256
Usable Host Addresses
254
Last Subnet Octet (255.255.255.X)
0

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About IPv4 Subnet Mask & CIDR Calculator

Calculate usable host IP count, wildcards, and netmask octets from CIDR prefix length (/0 to /32). Enter CIDR Prefix Length and the tool works out Total IP Addresses, Usable Host Addresses and Last Subnet Octet straight away. Everything runs in your browser, so your data never leaves your device.

How to use IPv4 Subnet Mask & CIDR Calculator

  1. Enter CIDR Prefix Length.
  2. Change any value to see the result update instantly.
  3. Read Total IP Addresses, Usable Host Addresses and Last Subnet Octet in the results panel — copy or download what you need.

Key features

  • Shows Total IP Addresses
  • Shows Usable Host Addresses
  • Shows Last Subnet Octet (255.255.255.X)
  • 1 adjustable input, results update as you type
  • No signup, no limits

Frequently asked questions

Is this calculation free and private?
Yes, 100% of calculations execute locally in your web browser. No inputs or personal data are stored or transmitted.
What does the IPv4 Subnet Mask & CIDR Calculator give me?
It works out Total IP Addresses, Usable Host Addresses and Last Subnet Octet, updating live as you change the inputs.
What do I need to enter?
Just CIDR Prefix Length. Every field has a sensible default you can start from.
Is my data uploaded anywhere?
No. The calculation runs in your browser with JavaScript — nothing you type is sent to a server or stored.
Does it work on a phone?
Yes. The layout adapts to small screens and needs no app or signup.

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IPv4 Subnet Mask & CIDR Calculator | TheToolss