Free CIDR Calculator – Calculate IP Ranges & Subnets Online

Calculate subnet masks, network addresses, broadcast addresses, and host ranges from CIDR notation. Instant IP range visualization with private/public classification. Free, browser-based networking tool.

What Is CIDR?

CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and IP routing. CIDR notation combines an IP address with its network prefix length (e.g., 192.168.1.0/24).

CIDR Notation Explained

192.168.1.0/24
└────┬────┘ └┬┘
     IP      Prefix (24 bits for network)

The prefix length indicates how many bits are used for the network portion. The remaining bits identify hosts within that network.

How to Use This Calculator

Step 1: Enter CIDR

Type a valid CIDR notation like 192.168.1.0/24.

Step 2: View Results

Instantly see:

Network and broadcast addresses
First and last usable hosts
Subnet and wildcard masks
Total and usable host count
IP classification

Step 3: Copy Results

Export the full analysis for documentation.

What Gets Calculated

Field	Description
Network Address	First IP in the range (network identifier)
Broadcast Address	Last IP in the range (all-hosts broadcast)
First Host	First usable host IP
Last Host	Last usable host IP
Subnet Mask	Dotted decimal mask (e.g., 255.255.255.0)
Wildcard Mask	Inverse of subnet mask
Total Hosts	All IPs in range including network/broadcast
Usable Hosts	Assignable host addresses

Common CIDR Prefixes

CIDR	Subnet Mask	Usable Hosts
/8	255.0.0.0	16,777,214
/16	255.255.0.0	65,534
/24	255.255.255.0	254
/25	255.255.255.128	126
/26	255.255.255.192	62
/27	255.255.255.224	30
/28	255.255.255.240	14
/29	255.255.255.248	6
/30	255.255.255.252	2
/31	255.255.255.254	2 (point-to-point)
/32	255.255.255.255	1 (single host)

Private IP Ranges (RFC 1918)

Range	CIDR	Typical Use
10.0.0.0 – 10.255.255.255	10.0.0.0/8	Large networks
172.16.0.0 – 172.31.255.255	172.16.0.0/12	Medium networks
192.168.0.0 – 192.168.255.255	192.168.0.0/16	Home/small office

Frequently Asked Questions

What's the difference between network and broadcast address?

The network address (first IP) identifies the network. The broadcast address (last IP) reaches all hosts on that network. Neither can be assigned to individual hosts.

Why are there fewer usable hosts than total IPs?

Two addresses are reserved: network address and broadcast address. Exception: /31 uses both for point-to-point links.

What's a wildcard mask?

The inverse of the subnet mask. Used in access control lists (ACLs) and routing protocols to match IP ranges.

Does this work for IPv6?

This calculator handles IPv4 only. IPv6 uses a different format.

CIDR Calculator