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IP Subnet Calculator

Calculate IPv4 and IPv6 subnets including network addresses, usable host ranges, subnet masks, IP ranges, and CIDR notation.

How to use: Choose IPv4 or IPv6, enter an IP address, select subnet mask or prefix length, and calculate subnet information including network range and usable hosts.
Subnet Calculation Results

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Understanding IP Subnetting and Network Addressing

IP subnetting is the process of dividing a network into smaller, more manageable sub-networks. This calculator supports both IPv4 and IPv6 protocols, helping network administrators plan and configure network infrastructure efficiently.

What is Subnetting?

A subnet is a division of an IP network, where an IP network uses the Internet Protocol suite (commonly known as TCP/IP). Subnetting allows network administrators to:

Key Concept: An IP address consists of a network portion (routing prefix) and a host portion (host identifier). Subnet masks and CIDR notation help define the boundary between these portions.

IPv4 vs IPv6

IPv4: Uses 32-bit addresses (e.g., 192.168.1.1) with subnet masks in dotted decimal notation (e.g., 255.255.255.0) or CIDR notation (e.g., /24).

IPv6: Uses 128-bit addresses (e.g., 2001:db8:85a3::8a2e:370:7334) with prefix lengths (e.g., /64) to define network boundaries.

CIDR Notation

Classless Inter-Domain Routing (CIDR) notation uses a slash followed by a number to indicate how many bits are used for the network portion. For example:

Common IPv4 Subnet Reference

CIDR Subnet Mask Usable Hosts
Class A Networks
/8255.0.0.016,777,214
/12255.240.0.01,048,574
Class B Networks
/16255.255.0.065,534
/20255.255.240.04,094
Class C Networks
/24255.255.255.0254
/25255.255.255.128126
/26255.255.255.19262
/27255.255.255.22430
/28255.255.255.24014
/29255.255.255.2486
/30255.255.255.2522

Practical Applications

Network Design: Subnetting helps create logical network segments for departments, VLANs, or geographic locations.

Security: Separate subnets can implement different security policies and access controls.

Performance: Smaller broadcast domains reduce network congestion and improve overall performance.

Pro Tip: When planning subnets, always account for network and broadcast addresses, which cannot be assigned to hosts. A /24 subnet has 256 total addresses but only 254 usable host addresses.