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IP Range to CIDR Calculator

Convert any start and end IPv4/IPv6 address range into the optimal minimal list of valid CIDR subnets. Fast and client-side.

CIDR Block(s) Required

💡 How to Convert an IP Range to CIDR

Calculate the perfect networking setup in three simple steps:

1

Enter Starting IP

Locate the exact first IP in the sequence you need to cover.

2

Enter Ending IP

Input the final IP address of the contiguous block you are targeting.

3

Calculate Blocks

Click Calculate and let the tool calculate the minimum CIDR notations to use.

📖 About IP Range to CIDR Calculator

What is the IP Range to CIDR Calculator?

The IP Range to CIDR Calculator is a network administration tool that converts a starting and ending IP address range into its equivalent Classless Inter-Domain Routing (CIDR) notation blocks. When an arbitrary range of IP addresses does not fit perfectly into a single subnet, this tool breaks the range down into the minimum possible number of valid CIDR routing prefixes.

Common Use Cases

  • Firewall Configuration: Most modern firewalls (like iptables, pfSense, AWS Security Groups) require network definitions to be formatted in CIDR notation instead of arbitrary IP ranges.
  • Routing Tables: When aggregating network routes, assigning VLANs, or implementing BGP announcements, network engineers must use accurately sized CIDR blocks.
  • Access Control Lists (ACLs): Cloud service providers and application servers restrict access based on IP, using CIDR blocks to permit or block specific clients.

Key Features

Optimal Calculations

The tool breaks down ranges into the fewest possible CIDR blocks required to strictly cover the exact start and end IPs without spilling over into unrequested addresses.

IPv4 Support

Instantly converts standard IPv4 ranges into valid IPv4 CIDR blocks.

100% Client-Side Processing

Calculations are performed directly in your browser without requiring server interaction. This guarantees extremely fast results and eliminates network latency.

Privacy & Security

This utility operates completely offline once loaded. Your entered IP addresses and network topologies are never transmitted to our servers or logged anywhere, ensuring your network infrastructure details remain entirely private.

❓ Frequently Asked Questions

It mathematically breaks down any arbitrary range of IP addresses into the absolute minimum number of valid routing prefixes (CIDR blocks) required to perfectly cover the range.
Yes! The calculations are entirely performed inside your web browser using JavaScript. We do not track, store, or log the IP addresses you enter into the tool.
Yes, our IP to CIDR tool seamlessly computes both standard IPv4 and expanded IPv6 address ranges.
Most modern firewalls, cloud infrastructure (like AWS Security Groups), and routing protocols require IP ranges to be specified mathematically as CIDR blocks. An arbitrary range (e.g., 192.168.1.5 to 192.168.1.15) cannot be represented by a single CIDR block and must therefore be split into multiple smaller blocks.

Version History

1.0.0

Initial release of IP Range to CIDR Calculator

Mar 01, 2026