IP Subnet Calculator

Calculate network address, broadcast address, subnet mask, wildcard mask, host range, and address counts based on four IP octets and a CIDR prefix. IP Subnet Calculator helps network administrators, engineers, students, and IT professionals plan and troubleshoot IPv4 networks.

Highlights

  • Calculate IPv4 network and broadcast addresses instantly.
  • Determine subnet and wildcard masks from any CIDR prefix.
  • View the first and last usable host addresses.
  • Find total and usable host address counts.
  • Display network bits, host bits, and CIDR notation.

Table of Contents

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

How IP Subnet Calculator Works?

The IP Subnet Calculator divides a valid IPv4 address into a network portion and a host portion using the CIDR prefix length. The four octets must each be integers from 0 through 255, while the CIDR prefix must be from 0 through 32.

The prefix length specifies the number of network bits. The remaining binary positions are host bits:

networkBits=prefixLength,hostBits=32-prefixLength

The subnet mask contains the selected number of leading 1 bits followed by 0 bits. The wildcard mask is the bitwise inverse of the subnet mask. The network address is found by applying a bitwise AND operation between the input IP address and the subnet mask. The broadcast address is found by combining the network address with the wildcard mask using a bitwise OR operation.

networkAddress=IPAddress∧subnetMask
broadcastAddress=networkAddress∨wildcardMask

The number of addresses in a subnet depends on the host-bit count:

totalAddresses=2hostBits

Under the conventional IPv4 host-allocation rule, the network and broadcast addresses are reserved, so the usual number of usable host addresses is:

usableHosts=2hostBits-2

For example, the default input 192.168.1.10/24 has 24 network bits and 8 host bits.


OutputResult
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
CIDR notation192.168.1.0/24
Total addresses256
Usable host addresses254

Practical Use Cases

Network administrators can enter an assigned IPv4 address and CIDR prefix to identify the subnet boundary, broadcast address, host range, and number of devices that can be addressed on a local network.

Network engineers can use the subnet mask and wildcard mask when designing routed networks, writing access control lists, and defining address groups in routing configurations.

IT support technicians can verify whether a device belongs to the expected network by comparing its network address, CIDR notation, and usable host range with the site configuration.

Students and trainees can test different prefix lengths to see how network bits, host bits, total addresses, and usable host addresses change as a subnet becomes larger or smaller.

Cloud and systems administrators can use the calculator when planning IPv4 address spaces for virtual networks, server segments, management networks, and isolated application subnets.

Security professionals can reference the calculated network and wildcard masks when grouping addresses for firewall rules, monitoring policies, and access-control entries.

Accuracy and Limitations

The calculator accurately applies standard 32-bit IPv4 CIDR calculations when all four octets are integers from 0 through 255 and the prefix length is from 0 through 32. It reports network and broadcast boundaries, masks, bit counts, total addresses, and the conventional usable-host range using the network-and-broadcast reservation rule. Prefixes /31 and /32 are special cases: /31 networks are commonly used for point-to-point links and /32 identifies a single address, so their operational host availability can differ from the conventional total-minus-two interpretation. The results do not determine whether an address is publicly routable, reserved for a special purpose, already in use, or permitted by a specific routing or security policy.

Quick Examples

Example #1: Small Office Network

Calculate the subnet range and host capacity for a typical small office IPv4 network.

Example #2: Corporate Department Network

Determine network boundaries and address capacity for a larger departmental subnet.

Example #3: Point-to-Point Link

Calculate the usable addresses for a small point-to-point network connection.

Frequently Asked Questions

A subnet is a logically divided portion of an IP network. Subnetting helps organize devices, manage address space, and control network traffic.

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

The network address identifies the subnet itself, while the broadcast address is used to send traffic to all devices within that subnet. Neither is normally assigned to an individual host.

The number of usable host addresses depends on the number of host bits. In most IPv4 subnets, two addresses are reserved for the network and broadcast addresses.

A wildcard mask identifies which IP address bits should be matched or ignored. It is commonly used in routing protocols and access control lists.

Cite This Calculator