CIDR Calculator

Calculate network addresses, broadcast addresses, subnet masks, host ranges, and address quantities based on an IPv4 address and prefix length. CIDR Calculator helps network engineers, system administrators, developers, and IT students plan and analyze IPv4 networks.

Highlights

  • Calculate IPv4 network and broadcast addresses from any CIDR prefix.
  • Determine subnet masks and wildcard masks instantly.
  • Identify the first and last usable host addresses.
  • Find total and usable host address counts for network planning.
  • View network and host bits for clearer CIDR analysis.

Table of Contents

  1. How CIDR Calculator Works?
  2. Practical Use Cases
  3. Accuracy and Limitations
  4. Quick Examples
  5. Frequently Asked Questions (FAQs)
  6. Cite This Calculator

How CIDR Calculator Works?

The CIDR Calculator analyzes an IPv4 address together with a prefix length from /0 through /32. The prefix length specifies how many of the 32 binary IPv4 bits belong to the network portion; the remaining bits identify addresses within that network.

networkBits=prefixLength
hostBits=32−prefixLength

The calculator first combines the four entered octets into a 32-bit IPv4 address. It then creates a subnet mask containing the selected number of leading binary 1s followed by 0s. The network address is found by applying a bitwise AND operation between the IPv4 address and the subnet mask. The broadcast address is the final address in the same range.

networkAddress=IPAddress∧subnetMask
broadcastAddress=networkAddress+totalAddresses−1

The number of addresses in the CIDR range depends on the host-bit count. The wildcard mask is the inverse of the subnet mask, so every network-mask 1 becomes 0 and every network-mask 0 becomes 1.

totalAddresses=2hostBits
wildcardMask=NOT(subnetMask)

For ordinary IPv4 subnets, the first usable address is the network address plus one, and the last usable address is the broadcast address minus one. The conventional usable-host calculation reserves those two boundary addresses.

usableHostAddresses=2hostBits−2

For example, an input of 192.168.1.10 with a prefix length of /24 produces the following results:


ResultValue
CIDR notation192.168.1.10/24
Network address192.168.1.0
Broadcast address192.168.1.255
Subnet mask255.255.255.0
Wildcard mask0.0.0.255
First usable address192.168.1.1
Last usable address192.168.1.254
Total addresses256
Usable host addresses254
Network bits24
Host bits8

Practical Use Cases

Network engineers can use the calculator to divide address space into appropriately sized subnets, identify network and broadcast boundaries, and verify that routing plans do not overlap.

System administrators can determine the subnet mask, assignable host range, and final broadcast address before configuring servers, gateways, firewalls, and other infrastructure devices.

Developers working on networking software can check CIDR parsing and access-control logic by comparing calculated network addresses, wildcard masks, and host ranges with expected IPv4 results.

IT students and certification candidates can practice converting prefix lengths into subnet masks, counting network and host bits, and validating the number of addresses available in common subnet sizes.

Security and firewall administrators can use the wildcard mask and CIDR range to build or review access control rules that include exactly the intended IPv4 addresses.

Cloud and infrastructure planners can estimate address capacity for virtual networks, application segments, management networks, and isolated service subnets before assigning devices or workloads.

Accuracy and Limitations

The calculator produces exact IPv4 bitwise results when all four octets are integers from 0 through 255 and the prefix length is an integer from 0 through 32. It calculates the conventional usable-host count by reserving the network and broadcast addresses; therefore, /31 point-to-point links and /32 host routes may require special interpretation because they do not follow the usual two-reserved-address model. The calculator supports IPv4 CIDR values only and does not account for overlapping networks, routing policy, DHCP reservations, firewall behavior, or whether an address is operationally available on a particular network.

Quick Examples

Example #1: Small Office Network

Plan a /24 private IPv4 network for a small office with up to 254 usable host addresses.

Example #2: Department Subnet

Calculate a smaller /26 subnet for a department, laboratory, or network segment requiring up to 62 usable hosts.

Example #3: Point-to-Point Link

Analyze a /30 subnet commonly used for a point-to-point connection between two network devices.

Frequently Asked Questions

CIDR notation combines an IPv4 address with a prefix length, such as 192.168.1.0/24. The prefix length indicates how many bits identify the network.

A typical /24 network contains 256 total addresses and 254 usable host addresses. The network and broadcast addresses are reserved.

The network address identifies the subnet itself, while the broadcast address sends traffic to all hosts within that subnet. Neither is normally assigned to an individual device.

A subnet mask identifies the network and host portions of an IPv4 address. A wildcard mask is its inverse and is commonly used in access control lists and routing rules.

Choose a prefix that provides enough host addresses for the devices in the subnet while avoiding unnecessary address space. A longer prefix creates a smaller subnet, while a shorter prefix creates a larger one.

Cite This Calculator