What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation represents IP ranges using a prefix, like 192.168.0.0/24, where /24 indicates the network has 256 addresses.

How do I calculate CIDR from IP range?

Enter the first and last IP of your range to find the CIDR block(s) that cover it. The tool calculates the optimal prefix length.

What is IP range aggregation?

Aggregation (supernetting) combines multiple smaller networks into a larger one to reduce routing table entries.

CIDR Calculator

Convert IP ranges to CIDR and expand CIDR blocks.

Start IP

End IP

CIDR Reference

CIDR	Subnet Mask	Total IPs	Usable
/32	255.255.255.255	1	1
/30	255.255.255.252	4	2
/28	255.255.255.240	16	14
/24	255.255.255.0	256	254
/16	255.255.0.0	65,536	65,534
/8	255.0.0.0	16,777,216	16,777,214

📘 How It Works

Range to CIDR

Calculates the CIDR blocks needed to exactly cover an IP range from start to end.

CIDR Expansion

Lists all IP addresses within a CIDR block (limited to /24 or smaller for display).

Range Calculation

Uses binary math to find the largest power-of-2 aligned blocks that fit within the range.

💡 Common Use Cases

Firewall Rules

Convert IP ranges to CIDR blocks for security group and ACL configurations.

Route Summarization

Aggregate multiple routes into fewer CIDR blocks to reduce routing table size.

IP Allocation

Plan and document IP address assignments using CIDR notation.

Cloud Networking

Define VPC subnets, peering ranges, and security policies in AWS/Azure/GCP.

Related Networking Tools Tools

Subnet Calculator → IP Converter → MAC Formatter → Bandwidth Calculator →