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How to Use the IP CIDR Calculator

Enter any IPv4 address and a prefix length (0–32) to instantly calculate all subnet properties.

Step 1

Enter an IPv4 Address

Type any IPv4 address such as 192.168.1.100. The tool validates the address against the RFC 791 specification.

Example Input

IP: 192.168.1.100
Prefix: 24
Step 2

Review the Calculated Results

The tool instantly calculates all subnet properties following CIDR (RFC 4632) standards.

Example Output

CIDR Notation:    192.168.1.0/24
Network Address:  192.168.1.0
Broadcast:        192.168.1.255
Subnet Mask:      255.255.255.0
Wildcard Mask:    0.0.0.255
First Usable IP:  192.168.1.1
Last Usable IP:   192.168.1.254
Total Hosts:      256
Usable Hosts:     254
Step 3

Apply Results in Your Network

Use the output for firewall rules, DHCP pool configuration, and routing table entries. Refer to IANA special-use ranges when planning private networks.

Step 4

Copy or Download

Use Copy to paste results into your config, or Download to save a reference file for documentation and handoff. For deeper address planning guidance, review ARIN IPv4 documentation.

Frequently Asked Questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length (e.g. 192.168.1.0/24) to define a subnet. The prefix length specifies how many bits form the network portion.

What is the difference between total and usable hosts?

Total hosts includes the network address and broadcast address. Usable hosts subtracts those two, leaving the range actually assignable to devices. For a /24 subnet: 256 total, 254 usable.

Does this support /31 and /32 prefixes?

Yes. /31 subnets (point-to-point links per RFC 3021) have 2 usable hosts. /32 represents a single host address.

Is my data sent to a server?

No. All calculations run entirely in your browser. Pair with IP Address Converter for full IPv4 format conversion.

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