CIDR to IP Range Converter

CIDR to IP Range Converter

Enter a CIDR block (e.g. 192.168.1.0/24) to see the full IP range, masks, host counts, and address type.

CIDR to IP Range Converter

What This Tool Does

This converter expands any IPv4 CIDR block into the numbers you actually need to use it. You get the first and last IP, network and broadcast addresses, subnet and wildcard masks, and host counts. The tool also identifies the address type. It flags private RFC 1918 space, carrier-grade NAT space, loopback, and link-local ranges automatically. Drop in 10.0.0.0/22 and you see a range of 10.0.0.0 through 10.0.3.255. That block holds 1,024 addresses and 1,022 usable hosts. For blocks of /20 and tighter, you can expand the full address list. That list pastes cleanly into a firewall rule, allowlist, or DHCP reservation.

CIDR Notation in Plain English

Classless Inter-Domain Routing (CIDR) notation is a compact way to describe an IP block. The slash number is the prefix length. It states how many of the 32 bits in an IPv4 address are locked to the network. Everything left over is free for hosts. A /24 reserves 24 bits for the network and leaves 8 bits for hosts. That works out to 256 total addresses. A /16 reserves only 16 bits and leaves 16 for hosts, giving you 65,536 addresses. The smaller the prefix number, the larger the block. For a deeper walk-through of prefix lengths, see our subnetting beginner’s guide. For a prefix-by-prefix breakdown of /8 through /32, read CIDR Notation Explained. To understand the dotted-decimal format itself, read IP address formats explained.

When You’d Use a CIDR Range Converter

Engineers reach for this tool when software demands explicit values instead of notation. A human writes 10.0.0.0/22 on the whiteboard; the SaaS allowlist wants a literal start and end IP. AWS security groups, pfSense and OPNsense firewall rules, and Cisco ACLs usually accept either form. Cloud bucket policies, SaaS dashboards, and legacy systems frequently do not. Other common uses include overlap checks against existing assignments and generating scan lists for audits. It also helps verify documentation handed off by another team. The tool pairs naturally with our subnet calculator when you need to subdivide a block. Use the IP-to-binary converter to see the math behind each octet. When the subdivisions are uneven, our VLSM and supernetting guide covers the technique.

Cloud Subnets Lose More Than Two Addresses

Classic subnet math reserves two addresses: network and broadcast. Cloud platforms reserve more. AWS holds the first four addresses and the last one in every VPC subnet. In a 10.0.0.0/24 subnet, AWS reserves .0 (network), .1 (VPC router), .2 (DNS), .3 (future use), and .255 (broadcast). A /24 therefore yields 251 usable hosts in AWS, not 254. AWS also bounds subnet sizes between /28 and /16. The results table below shows both the classic count and the AWS-adjusted count. Size cloud subnets with that smaller number, or your capacity math runs five short.

Reading the Results

  • Network address is the first address in the block. It identifies the subnet itself and is not assigned to a host on most networks.
  • Broadcast address is the last address. It is reserved for sending to every host in the subnet at once, so it is also unassignable.
  • Subnet mask is the dotted-decimal form of the prefix (a /24 is 255.255.255.0). Wildcard mask is its inverse, used in Cisco ACLs and OSPF statements.
  • First / last usable host bracket the addresses you can actually hand to devices. For a /24, that is the network address plus one through the broadcast minus one.
  • Total addresses includes the network and broadcast. Usable hosts excludes them. The exceptions are /31 point-to-point links per RFC 3021 and /32 single hosts.
  • Address type identifies the block’s range. It distinguishes private (RFC 1918), shared CGNAT (RFC 6598, 100.64.0.0/10), loopback, link-local, and public space.

Frequently Asked Questions

How many usable IP addresses are in a /24?

A /24 contains 256 total addresses and 254 usable hosts. The network and broadcast addresses are reserved. In an AWS VPC subnet, only 251 are usable because AWS reserves the first four addresses and the last one.

What does the slash number in CIDR notation mean?

The slash number is the prefix length. It states how many of the 32 bits in an IPv4 address identify the network. The remaining bits identify hosts. A smaller prefix number means a larger block: a /16 holds 65,536 addresses, while a /24 holds 256.

Why can’t I assign the first and last addresses in a subnet?

The first address is the network address, which identifies the subnet itself. The last is the broadcast address, used to reach every host at once. Two exceptions exist: /31 point-to-point links (RFC 3021) use both addresses, and a /32 is a single host.

Related Tools & Resources

Need to subdivide a block instead of just expand it? Use the subnet calculator. To check what’s live in your range, run a DNS lookup or find your public IP. See how IPv4 fits with IPv6 in our IPv4 vs. IPv6 guide. Need every mask from /0 to /32 at a glance? See the Subnet Mask Cheat Sheet. Look up any unfamiliar term in the Networking Glossary, or browse the full networking tools hub for everything in one place.

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