Subnet Calculator

Free IPv4 and CIDR tool for instant network calculations

Developer ToolsLaunched Oct 2026

The story

Subnet Calculator is a free online tool that instantly calculates network details for any IPv4 or IPv6 address and CIDR prefix. Get the network address, subnet mask, broadcast address, wildcard mask, usable host range, and binary representation in seconds. The tool features visual representation of network and host bits, interactive CIDR prefix adjustment, and step-by-step learning guides for understanding IP addressing and subnetting.

Overview

Subnet Calculator is a free web-based utility designed for network administrators, IT professionals, and students who need to quickly calculate and understand IPv4 and IPv6 subnetting. The tool accepts an IP address and CIDR prefix, then instantly displays comprehensive network details including the network address, subnet mask, broadcast address, wildcard mask, total addresses, usable hosts, and binary representation. Users can interactively adjust the CIDR prefix using a draggable slider or arrow keys to see results update in real time. The calculator includes additional utilities such as an IP Range Calculator for reading inclusive address ranges, a Subnet Splitter for dividing networks into smaller subnets, a Subnet Merger for finding the smallest subnet containing multiple networks, and an IP Address Converter for converting between decimal, binary, hexadecimal, and CIDR formats. The platform also provides educational resources including step-by-step guides on subnetting fundamentals, CIDR notation, subnet calculation methods, and Variable Length Subnet Masking (VLSM), making it suitable for both quick calculations and learning.

Key features

Instant Network Calculations

Enter any IPv4 or IPv6 address with CIDR prefix to instantly get network address, subnet mask, broadcast, wildcard mask, and usable host range.

Interactive Visual Representation

Drag a slider or use arrow keys to adjust the CIDR prefix and watch network and host bits update in real time with visual feedback.

Binary Representation

View the complete binary breakdown of IP addresses and subnet masks in both grouped and continuous formats.

Additional Subnet Tools

Access IP Range Calculator, Subnet Splitter, Subnet Merger, and IP Address Converter for comprehensive subnetting operations.

CIDR Reference Table

Quick reference table showing common IPv4 CIDR prefixes from /24 to /32 with subnet masks, total addresses, and usable hosts.

Educational Guides

Step-by-step learning resources covering subnet basics, CIDR notation, subnet calculation methods, and advanced VLSM techniques.

Use cases

1
Network Administrators
Quickly calculate subnet details for network design, static routes, and firewall configuration without manual calculations.
2
IT Professionals
Verify IP addressing schemes, plan subnets for infrastructure, and troubleshoot network allocation issues efficiently.
3
Students and Learners
Understand IP addressing fundamentals through interactive tools and comprehensive guides on subnetting concepts.
4
DevOps and Cloud Engineers
Calculate CIDR ranges for cloud infrastructure, container networking, and infrastructure-as-code configurations.

FAQ

What is a subnet?

A subnet is a contiguous block of IP addresses that share the same network prefix. The prefix length indicates how many leading bits are the network, with remaining bits distinguishing hosts within that block.

What does CIDR notation mean?

CIDR notation writes an address and prefix length, such as 192.168.1.0/24. The /24 means the first 24 bits are the network, corresponding to subnet mask 255.255.255.0.

How do I calculate usable hosts?

For conventional IPv4 prefixes /0 through /30, usable hosts equal 2 to the power of host bits, minus 2 (for network and broadcast addresses). A /24 has 8 host bits, yielding 256 total addresses and 254 usable hosts.

What is the difference between /30 and /31?

A /30 has 4 addresses and 2 usable hosts. A /31 also has 2 addresses but per RFC 3021, both function as hosts on point-to-point links, making it an exception to the standard rule.

Which value should I use in a static route?

Use the network address and prefix, such as 192.168.1.0/24. The usable range is for host assignment; the broadcast address is neither a next hop nor an assignable host.