Subnet Calculator

Input Method

CIDR Notation Subnet Mask

IP Address

CIDR Prefix Length

(subnet mask)

Subnet Mask

/ (CIDR notation)

Subnet Calculation Results

IP Address:

CIDR Notation:

Subnet Mask:

Network Class:

Network Address:

Broadcast Address:

First Usable Host:

Last Usable Host:

Total Hosts:

Usable Hosts:

Binary Subnet Mask:

Host IP Range

Understanding Subnetting

Subnetting is the practice of dividing a network into smaller logical subnetworks. This is essential for network management, security, and efficient address allocation. Our subnet calculator helps you determine key network parameters:

Key Terms

IP Address: A unique identifier for a device on a network (e.g., 192.168.1.1)
CIDR (Classless Inter-Domain Routing): A notation that specifies network size using a suffix showing the number of bits in the subnet mask (e.g., /24)
Subnet Mask: A 32-bit number that separates the network and host portions of an IP address
Network Address: The first address in a subnet, used to identify the network
Broadcast Address: The last address in a subnet, used to send data to all devices on the network
Host Range: The range of valid IP addresses that can be assigned to devices

CIDR to Subnet Mask Reference

CIDR	Subnet Mask	Usable Hosts
/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

Subnet Calculation Formula

Understanding the math behind subnetting helps in network planning:

Total hosts: 2^(32-CIDR)
Usable hosts: 2^(32-CIDR) - 2 (subtracting network and broadcast addresses)
Subnets created when dividing a network: 2^{(New CIDR - Original CIDR)}

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Common Subnet Applications

Proper subnet planning is crucial for network administrators and IT professionals. Here are some common subnetting scenarios and their benefits:

Network Security

Subnetting allows for the creation of separate network segments with different security policies. This helps contain security breaches and limits the spread of attacks within a network.

Network Performance

By dividing a large network into smaller subnets, broadcast traffic is reduced, leading to better overall network performance and reduced congestion on busy network segments.

Geographic Organization

Organizations with multiple locations often assign different subnets to each office, simplifying network management and routing between locations.

Department Segmentation

Different departments within an organization (e.g., Finance, HR, Engineering) can be assigned to different subnets, allowing for more granular access control and resource allocation.

IPv4 vs. IPv6 Subnetting

While this calculator focuses on IPv4 addresses, it's important to note that IPv6 uses a different subnetting approach:

IPv4 Subnetting

32-bit addresses
CIDR notation /0 to /32
Limited address space
Often requires careful planning

IPv6 Subnetting

128-bit addresses
CIDR notation /0 to /128
Virtually unlimited address space
Generally uses /64 for most networks