CIDR Calculator

Enter an IP address and prefix length or subnet mask to instantly calculate subnet details.

Last updated: May 29, 2026

IP Address

Prefix / Subnet Mask

IP Address	192.168.1.0
Subnet Mask	255.255.255.0
Wildcard Mask	0.0.0.255
Network Address	192.168.1.0
Broadcast Address	192.168.1.255
First Usable Host	192.168.1.1
Last Usable Host	192.168.1.254
Usable Hosts	254
Total Addresses	256
IP Class	C
CIDR Notation	192.168.1.0/24

// Binary representation

IP: 11000000.10101000.00000001.00000000

Mask: 11111111.11111111.11111111.00000000

Network: 11000000.10101000.00000001.00000000

Client-Side Processing

Input Data Stays on Device

Instant Local Execution

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What is CIDR Calculator?

CIDR Calculator computes all subnet information from a CIDR (Classless Inter-Domain Routing) notation. Given an IPv4 address and either a prefix length (/24) or dotted subnet mask (255.255.255.0), it calculates the network address, broadcast address, first and last usable host, number of usable hosts, wildcard mask, and binary representations. Supports all prefix lengths from /0 to /32.

How to Use CIDR Calculator

Enter an IPv4 address.

Enter a prefix length (e.g. 24) or subnet mask (e.g. 255.255.255.0).

Results appear instantly.

Common Use Cases

Planning IP address allocation for a network segment.
Verifying subnet boundaries when configuring firewalls or routers.
Learning subnetting and CIDR notation for networking certifications.
Checking how many hosts fit in a given subnet before provisioning.

Example Input and Output

CIDR /24 calculation for 192.168.1.0.

IP=192.168.1.0, Prefix=/24

IP: 192.168.1.0
Prefix: /24

Subnet details

Network: 192.168.1.0
Broadcast: 192.168.1.255
Hosts: 192.168.1.1 – 192.168.1.254
Usable: 254

Privacy

All calculations run locally in the browser.

Frequently Asked Questions

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation expresses a network as an IP address followed by a slash and prefix length (e.g. 192.168.1.0/24). The prefix length indicates how many bits are in the network portion of the address.

Can I enter a subnet mask instead of a prefix?

Yes. Enter the subnet mask in dotted-decimal format (e.g. 255.255.255.0) in the Prefix field. The calculator converts it to a prefix length automatically.

What are /31 and /32 subnets?

/32 is a host route (single IP, no broadcast). /31 is a point-to-point link (2 addresses, both usable per RFC 3021).

Is my data uploaded?

No. All calculation runs in your browser.