What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its network prefix length together, for example, 192.168.1.0/24, where /24 means the first 24 bits are the network identifier.

Is my data sent to a server?

No. All calculations are pure JavaScript bit arithmetic running in your browser.

How many usable hosts are in a /24 network?

A /24 network contains 256 addresses. Subtract 2 (network and broadcast addresses) for 254 usable host addresses.

Does the tool support IPv6?

The current version supports IPv4 CIDR notation. IPv6 support is planned for a future update.

CIDR / subnet calculator

CIDR calculator is a networking tool that derives subnet details from any IPv4 CIDR notation. It returns the network address, broadcast address, subnet mask, first and last usable hosts, and the total host count for any prefix from /0 to /32. The tool runs in your browser.

CIDR block

Network address	192.168.1.0
Broadcast address	192.168.1.255
Subnet mask	255.255.255.0
First usable host	192.168.1.1
Last usable host	192.168.1.254
Usable hosts	254
Total addresses	256
IP class	C

/24 · 255.255.255.0 · 254 usable hosts

Dedicated pages

Direct links for subnet and CIDR topics.

Subnet calculator

Calculate subnet details from CIDR notation. Get network address, broadcast, host range, subnet mask and usable hosts. Free, in-browser.

IP subnet mask calculator

Calculate subnet masks, network addresses and host ranges from any IP and prefix length. Free, in-browser, nothing uploaded.

CIDR notation calculator

Understand and calculate CIDR notation. Enter any CIDR block to see the IP range, subnet mask, and host count. Free, in-browser tool.

How to use the CIDR calculator

Enter a CIDR notation address, for example, 192.168.1.0/24 or 10.0.0.0/8.
The tool calculates network address, broadcast address, subnet mask, first and last host, and total host count.
Use the dual-input mode to enter an IP address and prefix length separately.
Copy any value from the results table to use in your network configuration.

Common uses

Planning subnets and IP address ranges for network infrastructure, using a byte converter for bandwidth calculations
Checking how many hosts a specific CIDR block can accommodate
Verifying that an IP address falls within a given network range, and use the number base converter to translate subnet masks between decimal and binary

Technical specification

Algorithm or formula: Bitwise math on a 32-bit unsigned integer view of the IP. Network = ip & mask, broadcast = network | ~mask, total hosts = 2^(32 − prefix), usable hosts = total − 2 for prefixes 0 to 30.
Browser API or library: Pure JavaScript bitwise operations. No external library.
Input limits: IPv4 CIDR notation only (e.g. 10.0.0.0/8 to 192.168.1.5/32).
Output: Network and broadcast addresses, subnet mask (dotted decimal), first and last host, total host count, and IP class designation (A, B, C, D, E).
Known limitations: IPv6 is not yet supported. Variable-length subnet masking (VLSM) helper output is not included.

Frequently asked questions

What is CIDR notation?: CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its network prefix length together, for example, 192.168.1.0/24, where /24 means the first 24 bits are the network identifier.
Is my data sent to a server?: No. All calculations are pure JavaScript bit arithmetic running in your browser.
How many usable hosts are in a /24 network?: A /24 network contains 256 addresses. Subtract 2 (network and broadcast addresses) for 254 usable host addresses.
Does the tool support IPv6?: The current version supports IPv4 CIDR notation. IPv6 support is planned for a future update.

Reviewed and tested May 25, 2026.