About The CIDR to IP Range

The CIDR to Range tool converts an IPv4 CIDR block into its full network range, first usable host, last usable host, total address count, and usable host count. It is useful when you need to turn compact CIDR notation into concrete boundaries for firewall rules, routing notes, cloud network planning, or documentation.

The calculation runs in the browser. If the IP portion is a host address inside the CIDR block, the tool normalizes it to the correct network range for the prefix.

How to Convert CIDR to an IP Range Online

1. Enter an IPv4 CIDR value, such as 10.0.4.77/20.
2. Click Calculate Range.
3. Review the network range, first usable host, last usable host, total addresses, and usable hosts.
4. Copy the output for firewall rules, VPC documentation, network tickets, or access reviews.

Reading the Results

Network range:
The full address span from the calculated network address to the broadcast address.

Usable hosts:
For most IPv4 CIDR blocks, usable hosts exclude network and broadcast addresses. /31 and /32 are treated as usable special cases.

Input normalization:
A value like 10.0.4.77/20 can produce a range beginning at 10.0.0.0 because the entered IP sits inside that larger block.

Common Use Cases

• Expanding cloud VPC, subnet, or security group CIDR values into visible ranges.
• Checking whether an IP falls inside a documented IPv4 block.
• Preparing firewall, router, or access-control notes.
• Teaching or verifying IPv4 subnet boundaries.

Quick FAQ

Does this support IPv6 CIDR blocks?
No. This tool is for IPv4 CIDR ranges unless the page explicitly says otherwise.

Why does the range start before the IP I entered?
CIDR blocks start at the network address. A host IP inside the block is rounded down to the containing network.

Does this make a network request?
No. CIDR range calculation is local math in the browser.

What happens with a high prefix value?
A high prefix such as /32 represents a very small range, often a single IPv4 address.