Enter an IPv4 CIDR block — prefix /0 to /32
Quick examples:
Ready to expand
Enter a CIDR block and click Expand// expand cidr blocks into full ip address lists
Expand any CIDR notation into a full list of IP addresses. View network address, broadcast, usable range, subnet mask, and every IP in small blocks.
Ready to expand
Enter a CIDR block and click ExpandType any valid IPv4 CIDR block like 192.168.1.0/24 or pick a quick example above.
Hit the Expand CIDR button or press Enter. The tool calculates your subnet instantly.
Copy the full IP list, download as .txt, or use the summary to understand your network.
CIDR (Classless Inter-Domain Routing) notation represents a block of IP addresses as a base address and a prefix length, like 192.168.1.0/24. This tool decodes that notation into every individual IP address in the range, plus subnet details like the network address, broadcast address, subnet mask, and usable host count.
CIDR (Classless Inter-Domain Routing) notation uses a slash followed by a number to denote how many bits are the network part of an IP address. For example, 192.168.1.0/24 means the first 24 bits are the network, leaving 8 bits for hosts — which gives 256 total IPs (254 usable).
The network address is the first IP in a CIDR block and identifies the subnet itself — it cannot be assigned to a host. The broadcast address is the last IP and is used to send packets to all devices on the subnet. Neither can be used as a regular host IP.
Every subnet reserves two IPs: the network address (first IP) and the broadcast address (last IP). So a /24 block with 256 total addresses provides 254 usable IPs. A /30 block has 4 total IPs, leaving just 2 usable for point-to-point links. A /32 is a single host with no usable range.
A subnet mask is an alternate representation of the CIDR prefix in dotted-decimal notation. For a /24, the subnet mask is 255.255.255.0 — the 1-bits indicate the network portion and the 0-bits indicate the host portion. It's commonly used in older network configurations and firewall rules.
A /16 block contains 65,536 IPs. Blocks larger than that (/15, /8, etc.) can contain millions or billions of addresses, which would freeze your browser. For large blocks, this tool still shows all the summary information — network address, broadcast, mask, and host count — without listing every individual IP.
A wildcard mask is the inverse of a subnet mask. Where a subnet mask has 1s for network bits and 0s for host bits, a wildcard mask has 0s for fixed bits and 1s for variable bits. Wildcard masks are commonly used in Cisco ACLs and OSPF configurations. For a /24, the wildcard mask is 0.0.0.255.
Yes. This tool works with all RFC 1918 private ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. It also works with public IP ranges, loopback (127.0.0.0/8), link-local (169.254.0.0/16), and multicast ranges.
Currently this tool supports IPv4 CIDR notation only (/0 through /32). IPv6 support (e.g. 2001:db8::/32) is planned for a future version. For IPv6 range expansion, you would need a dedicated IPv6 subnet calculator due to the vastly larger address space.
A CIDR range expander is a tool that takes a CIDR (Classless Inter-Domain Routing) block — like 192.168.1.0/24 — and enumerates every individual IP address contained within it. Beyond simply listing IPs, a good CIDR expander also decodes the subnet's key properties: the network address, broadcast address, subnet mask, wildcard mask, and the total and usable host counts.
Network engineers, system administrators, DevOps teams, and developers use CIDR expanders constantly. Whether you're writing firewall rules, configuring AWS security groups, auditing IP allocations, or just learning how subnetting works, being able to visualize the actual IP addresses inside a CIDR block is invaluable.
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CIDR notation was introduced in 1993 (RFC 1519) to replace the older classful network addressing (Class A, B, C). It represents an IP block as two parts separated by a slash: the base IP address and the prefix length. The prefix length (also called the subnet mask length) tells you how many of the 32 bits in an IPv4 address are used for the network portion.
For example, 10.0.0.0/8 means the first 8 bits (10) are fixed as the network identifier, leaving 24 bits for host addresses. That's 2²⁴ = 16,777,216 total addresses — the entire Class A range once known as "10.x.x.x". In contrast, 192.168.1.0/30 has only 4 addresses (2 usable), making it ideal for point-to-point links where you only need to connect two devices.
Every CIDR block has three special categories of addresses:
192.168.1.0 for a /24). This identifies the subnet itself and is never assigned to a host device. Routers use it to identify the network when building routing tables.192.168.1.255 for a /24). Packets sent to this address are delivered to all hosts on the subnet. Like the network address, it cannot be assigned to an individual host.192.168.1.1 through 192.168.1.254 — 254 addresses. The formula is always 2^(32-prefix) - 2.The same prefix length can be expressed in two different mask formats, each used in different contexts:
The subnet mask (also called the network mask) represents the network bits as 1s and the host bits as 0s. A /24 prefix becomes 255.255.255.0. Subnet masks are used in traditional network configuration, Windows/Linux interface settings, and many older router configurations. When you configure an IP address on a network interface, you typically supply both the IP and its subnet mask.
The wildcard mask is the bitwise inverse of the subnet mask — host bits are 1 and network bits are 0. A /24 becomes 0.0.0.255. Wildcard masks are predominantly used in Cisco access control lists (ACLs) and OSPF/EIGRP configurations. They define which bits to ignore when matching IP addresses in routing rules.
Here is a quick reference for the most commonly used CIDR prefix lengths in IPv4 networking:
10.x.x.x space.CIDR range expansion is a fundamental operation across many networking and DevOps workflows:
RFC 1918 reserves three blocks of IPv4 address space for private networks that should never be routed on the public internet:
10.0.0.0/8 — 16.7 million addresses. Common in large enterprises and cloud VPCs.172.16.0.0/12 — 1 million addresses. Often used in mid-size organizations; ranges from 172.16.0.0 to 172.31.255.255.192.168.0.0/16 — 65,536 addresses. The most common home and small office range, typically further divided into /24 subnets.When planning a new network, these private ranges are your starting point. This CIDR expander helps you carve them up into appropriately-sized subnets for different network segments, VLANs, or availability zones.
IPv6 also uses CIDR notation, but with 128-bit addresses instead of 32-bit. A typical IPv6 allocation might be a /48 (which contains 2⁸⁰ addresses — more than the entire IPv4 address space many times over) or a /64 for a single network segment. While this tool currently handles IPv4 only, the conceptual model is identical: prefix length determines how much of the address is fixed for the network, and the rest is the host portion.