CIDR / Subnet Host Calculator
Fill in the value and the answer updates as you type.
How the CIDR / Subnet Host Calculator works
Total addresses = 2^(32 − prefix). Usable hosts normally subtract the network and broadcast addresses, so a /24 has 256 addresses and 254 usable hosts. /31 links use both addresses and /32 is a single host. Example: with the default values, subnet mask comes to 255.255.255.0.
Inputs and results
The CIDR / Subnet Host Calculator takes 1 input and gives 4 results.
What you enter
- CIDR prefix length (/) — starts at 24.
What you get
- Subnet mask
- Wildcard mask
- Total addresses
- Usable hosts
Example: CIDR / Subnet Host Calculator with the starting values
With cidr prefix length 24 /, the calculator returns:
| Subnet mask | 255.255.255.0 |
|---|---|
| Wildcard mask | 0.0.0.255 |
| Total addresses | 256 |
| Usable hosts | 254 |
Change any value above and the results update straight away.
CIDR / Subnet Host Calculator FAQ
How do I use the CIDR / Subnet Host Calculator?
Enter cidr prefix length in the fields, then read subnet mask, wildcard mask, total addresses and usable hosts in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the CIDR / Subnet Host Calculator calculate?
Subnet mask and usable host count for a CIDR prefix. It returns subnet mask, wildcard mask, total addresses and usable hosts from the 1 value you provide.
What values does the CIDR / Subnet Host Calculator start with?
It opens with cidr prefix length 24 / so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the CIDR / Subnet Host Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the CIDR / Subnet Host Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.