What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation is a compact way to represent an IP address and its associated network mask. For example, 192.168.1.0/24 means the first 24 bits are the network portion, leaving 8 bits for host addresses (256 total addresses, 254 usable).

How do I calculate the number of hosts in a CIDR range?

For IPv4, the formula is 2^(32 - prefix length). A /24 gives 2^8 = 256 total addresses. Subtract 2 for the network and broadcast addresses to get 254 usable host addresses. A /16 gives 65,536 total addresses (65,534 usable).

What is the difference between a subnet mask and a wildcard mask?

A subnet mask marks the network bits with 1s and host bits with 0s (e.g., 255.255.255.0 for /24). A wildcard mask is the inverse — host bits are 1s and network bits are 0s (e.g., 0.0.0.255 for /24). Wildcard masks are commonly used in ACLs and routing configurations.

Does this tool support IPv6 CIDR ranges?

Yes! This tool supports both IPv4 and IPv6 CIDR notation. Enter an IPv6 CIDR like 2001:db8::/32 to see the full network details including the expanded address, prefix information, and network boundaries.

Can I check if a specific IP address belongs to a CIDR range?

Yes. Use the IP Lookup tab to enter an IP address and one or more CIDR ranges. The tool will instantly tell you which ranges contain that IP address, making it easy to verify firewall rules, ACLs, or routing tables.

Free Online CIDR Range Expander & Subnet Calculator (No Signup)

Expand CIDR ranges, calculate subnets, check IP membership, compare networks, split subnets, and visualize address space. Supports IPv4 and IPv6.

How to Use This Tool

Enter a CIDR range — Type a notation like 192.168.1.0/24 or 2001:db8::/32 into the Expander tab input field.
View network details — See the network address, broadcast, subnet mask, wildcard mask, usable host range, and total addresses.
Browse all IPs — Expand the range to list every IP address with binary and decimal views.
Use additional tabs — Check IP membership in a range, compare two networks side by side, or split a subnet into smaller blocks.

Common Use Cases

How many usable IPs are in my subnet? Enter your CIDR notation to instantly see the total addresses and usable host range after removing network and broadcast addresses.
Does this IP belong to a specific network? Use the IP Lookup tab to check if any IP address falls within a given CIDR range.
How do I split a large subnet into smaller ones? Use the Split/Join tab to divide a CIDR block into equal-sized subnets for network segmentation planning.

Split Subnet

Split a CIDR range into smaller subnets.

Aggregate / Summarize

Find the smallest CIDR that contains all given IPs or ranges.

🌐 CIDR Range Expander

How to Use This Tool

Common Use Cases