CIDR → IP Range Converter

The CIDR to IP Range Converter transforms CIDR notation into explicit start and end IP addresses, making it easy to see the exact boundaries of any subnet. Enter 10.0.0.0/8 and instantly see the range 10.0.0.0 to 10.255.255.255, or enter 192.168.1.0/28 to see the range 192.168.1.0 to 192.168.1.15 with 16 total addresses.

Understanding CIDR and IP Ranges

CIDR notation is compact and precise, but it is not always intuitive. When someone writes 172.16.0.0/12, an experienced network engineer can mentally compute that the range runs through 172.31.255.255, but most people -- including sysadmins who work more with servers than with routing -- need to see the actual start and end addresses to understand what is covered. This is especially true for non-standard prefix lengths like /20 or /13 where the boundaries fall in the middle of an octet and are not obvious at a glance.

The fundamental math is straightforward. A CIDR block with prefix length /n has 2^(32-n) total addresses for IPv4. The start address is the network address with all host bits set to zero, and the end address has all host bits set to one. For a /24, that means 256 addresses from .0 through .255. For a /20, that means 4,096 addresses, and the boundaries depend on where the network address sits in the address space. The converter does this calculation instantly so you do not have to work through binary arithmetic.

Beyond just showing the range, this tool also displays the usable host range (excluding the network and broadcast addresses), the subnet mask in dotted decimal, and the total address count. This makes it a quick reference for verifying that a CIDR block covers what you expect before you commit it to a firewall rule, DHCP scope, or network diagram.

How to Convert CIDR to an IP Range

1. Enter a valid CIDR block (e.g., 10.0.0.0/8 or 192.168.100.0/24)
2. The tool instantly displays the first address (network address) and last address (broadcast address for IPv4)
3. Review the usable host range, total address count, and subnet mask in dotted decimal
4. Copy the range for use in legacy firewalls, DHCP scopes, network scanners, or documentation

CIDR to IP Range Conversion Examples

Additional Details Displayed

For each CIDR block, the tool also calculates:

• Network address -- the first address in the block (all host bits set to 0)
• Broadcast address -- the last address in the block (all host bits set to 1, IPv4 only)
• Usable host range -- first usable to last usable (excludes network and broadcast for IPv4)
• Subnet mask -- dotted decimal form (e.g., 255.255.255.0 for /24)
• Total addresses -- 2^(32-prefix) for IPv4

When to Use the CIDR to IP Range Converter

• Legacy firewall configuration -- older firewalls and access control systems accept start-end ranges rather than CIDR notation
• DHCP scope setup -- defining DHCP scopes often requires specifying the first and last address in the range
• Network scanning -- tools like Nmap accept CIDR but others require explicit start-end ranges
• Documentation and reporting -- explicit ranges are clearer for stakeholders who are not familiar with CIDR notation
• IP address database queries -- geolocation and WHOIS databases sometimes use integer or range-based lookups
• Verification -- quickly confirm that a CIDR block you are about to deploy covers exactly the addresses you intend

How CIDR Notation Maps to IP Ranges

CIDR notation combines a network address with a prefix length that specifies how many leading bits are fixed. The remaining bits define the host portion.

Calculating the Range from CIDR

For a CIDR block like 192.168.1.0/24:

• The prefix /24 means the first 24 bits are the network portion
• The remaining 32 - 24 = 8 bits are the host portion
• The start address is the network address with all host bits set to 0: 192.168.1.0
• The end address has all host bits set to 1: 192.168.1.255
• Total addresses: 2^8 = 256

Bitwise Calculation Example

For 172.16.0.0/20:

Network:    10101100.00010000.0000|0000.00000000  (172.16.0.0)
                                  ^^^^
                         20 fixed bits | 12 host bits

Start:      10101100.00010000.00000000.00000000  (172.16.0.0)
End:        10101100.00010000.00001111.11111111  (172.16.15.255)

Total addresses: 2^12 = 4,096
Usable hosts:    4,094 (excluding network and broadcast)

Common Prefix Lengths

Practical Tips for Working with CIDR Ranges

One of the most common reasons to convert CIDR to a range is to enter the addresses into a system that does not support CIDR notation. Before you do this, check whether the system actually needs the full start-end range or just the usable host range. DHCP scopes, for example, typically should not include the network and broadcast addresses. If you configure a DHCP scope from .0 to .255 on a /24, some DHCP servers will attempt to hand out the network and broadcast addresses, which can cause subtle issues. Use the usable host range (.1 to .254 for a /24) instead.

When documenting networks for non-technical stakeholders, explicit ranges are much easier to understand than CIDR notation. Saying "our office network covers 192.168.1.0 through 192.168.1.255" is immediately clear, while "our office uses 192.168.1.0/24" requires the reader to understand prefix lengths. For internal engineering documentation, stick with CIDR notation since it is more precise and standard.

If you are working with non-standard prefix lengths like /20 or /22, always verify the boundaries before deploying. It is easy to assume that a /20 starting at 172.16.0.0 ends at 172.16.19.255 (which would be 20 times 256), but the actual end is 172.16.15.255 because CIDR works in powers of two, not multiples of octets. This converter eliminates that guesswork entirely.

Frequently Asked Questions

What is the difference between the total addresses and usable hosts?

In IPv4 subnetting, the first address (network address) and last address (broadcast address) are reserved and cannot be assigned to hosts. A /24 has 256 total addresses but only 254 usable hosts. The exceptions are /31 subnets (used for point-to-point links per RFC 3021) and /32 subnets (single host routes).

Does this tool support IPv6 CIDR notation?

Yes. Enter any IPv6 CIDR block like 2001:db8::/32 and the tool will display the full range from 2001:db8:: to 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff. IPv6 prefix lengths range from /0 to /128.

Why would I convert CIDR to a range instead of using CIDR directly?

Some systems and software do not accept CIDR notation. Older firewalls, certain DHCP servers, and some network scanning tools require explicit start and end addresses. Converting CIDR to a range also makes subnet boundaries easier to explain in documentation aimed at non-networking audiences.

What does a /32 CIDR block mean?

A /32 represents a single IP address. The start and end of the range are the same address. This is commonly used for host routes in routing tables or for specifying a single server in a firewall rule.

How do I know if my CIDR is in canonical form?

A CIDR block is in canonical (normalized) form when the host bits of the network address are all zero. For example, 192.168.1.0/24 is canonical, but 192.168.1.100/24 is not because the last octet should be 0 for a /24. The converter will still work with non-canonical input and will show you the correct range.

Related Tools

• IP Range to CIDR Converter - Convert an IP range back to minimal CIDR blocks
• CIDR Deaggregator - Expand a CIDR block into smaller blocks
• Range List to IP List - Expand IP ranges to individual IPs
• Smallest Covering CIDR (Two IPs) - Find the smallest CIDR that contains two IP addresses
• CIDR Normalizer - Normalize CIDR notation to canonical form