IP Subnet Calculator & CIDR Calculator

Free ToolVisual CalculatorNetwork Planning

My professional IP subnet calculator and CIDR calculator designed for network engineers and IT professionals. Calculate subnet masks, network addresses, broadcast addresses, and IP ranges instantly. Features visual subnet splitting and joining with real-time calculations.

IPv4 Support
CIDR Notation
Visual Splitting
Real-time Calc
/1665,536 IPs
/8/16/24/30
/16
192.168.0.0
Hosts
65,534
Mask
255.255.0.0
Complete Range
192.168.0.0→192.168.255.255
Usable Range
192.168.0.1→192.168.255.254

About IP Subnet Calculators

An IP subnet calculator is an essential tool for network administrators and engineers to plan and design network infrastructure. My advanced subnet calculator supports CIDR notation and provides visual feedback for complex subnetting scenarios.

Key Features

  • CIDR Calculator: Supports CIDR notation from /8 to /30 for IPv4 networks
  • Visual Subnet Splitting: Interactive splitting and joining of subnets
  • Real-time Calculations: Instant calculation of network addresses, subnet masks, and IP ranges
  • Broadcast Address Calculator: Automatic calculation of broadcast addresses
  • Usable IP Range: Shows first and last usable IP addresses in each subnet
  • Network Planning: Perfect for VLSM (Variable Length Subnet Masking) planning

Common Use Cases

Network Design

Plan IP address allocation for enterprise networks, data centers, and cloud infrastructure.

VLSM Planning

Implement Variable Length Subnet Masking for efficient IP address utilization.

Security Segmentation

Create network segments for improved security and traffic management.

Troubleshooting

Verify network configurations and diagnose connectivity issues.

Frequently Asked Questions

What is a subnet calculator and why do I need one?
A subnet calculator is a tool that helps network administrators calculate IP address ranges, subnet masks, network addresses, and broadcast addresses for a given CIDR block. It's essential for network planning, IP address management, and ensuring efficient use of IP address space in enterprise networks.
How do I calculate subnets using CIDR notation?
To calculate subnets using CIDR notation: 1) Enter your base network address (e.g., 192.168.1.0), 2) Set the CIDR mask (e.g., /24), 3) Click Calculate. The tool will show you the subnet mask, IP range, usable addresses, and network/broadcast addresses. You can then split the network into smaller subnets as needed.
What's the difference between network address and broadcast address?
The network address is the first IP address in a subnet range and identifies the network itself - devices cannot use this address. The broadcast address is the last IP address in the range, used to send messages to all devices in the subnet. Usable IP addresses are all addresses between these two.
Can I split subnets into smaller networks?
Yes! My visual subnet calculator allows you to split any subnet into two smaller subnets by clicking the Split button. This increases the CIDR mask by 1 (e.g., /24 becomes /25) and creates two equal-sized subnets. You can also join adjacent subnets of the same size using the Join button.
What CIDR ranges does this calculator support?
My subnet calculator supports CIDR ranges from /8 (16,777,214 usable IPs) to /30 (2 usable IPs). This covers everything from large enterprise networks to point-to-point links. The calculator automatically prevents invalid operations like splitting /31 networks.
Is this subnet calculator free to use?
Yes, this IP subnet calculator is completely free to use with no registration required. It works entirely in your browser, so your network information stays private. Use it for personal learning, professional network planning, or educational purposes.

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Technical Implementation Notes

Calculation Method

I use bitwise operations for accurate subnet calculations. Supports standard IPv4 addressing and CIDR notation as defined in RFC 4632.

Browser Compatibility

My calculator works in all modern browsers with JavaScript enabled. No plugins or additional software required. Mobile-responsive design for use on any device.