CIDR to IP Range Converter

CIDR to IP Range Converter

What This Tool Does

This converter takes any IPv4 CIDR block and expands it into the four numbers that actually matter when you go to use it: the first IP, the last IP, the network and broadcast addresses, and the total number of addresses inside the block. Drop in something like 10.0.0.0/22 and you immediately see that your range runs from 10.0.0.0 to 10.0.3.255, contains 1,024 addresses, and gives you 1,022 usable hosts. For small blocks (/24 and tighter), you can also expand the entire list of addresses so you can drop them 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 followed by a number (the prefix length) tells you how many of the 32 bits in an IPv4 address are locked to identify the network — everything else is free for hosts. A /24 reserves 24 bits for the network and leaves 8 bits for hosts, which works out to 256 total addresses. A /16 reserves only 16 bits for the network and leaves 16 for hosts, giving you 65,536 addresses. The smaller the prefix number, the larger the block. If you want a deeper walk-through of how prefix lengths work, see our subnetting beginner’s guide.

When You’d Use a CIDR Range Converter

Most network engineers reach for a CIDR-to-range converter when they need to translate a notation that humans wrote on a whiteboard into the explicit start and end values that a piece of software requires. AWS security groups, firewall rules in pfSense and OPNsense, and Cisco access control lists usually accept either form, but cloud bucket policies, allowlists in SaaS dashboards, and legacy systems frequently demand a literal IP range. Other common uses include verifying that a block does not overlap an existing assignment, generating a list of IPs to scan during an audit, and double-checking documentation handed off by another team. The tool pairs naturally with our subnet calculator when you need to subdivide a block, and with the IP-to-binary converter when you want to see the math behind each octet.

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.
• 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 — except for /31 (point-to-point links per RFC 3021) and /32 (single host) where the math is different.

Related Tools & Resources

Need to subdivide a block instead of just expand it? Use the subnet calculator. To check what’s actually live in your range, run a DNS lookup, find your public IP, or see how IPv4 fits with IPv6 in our IPv4 vs. IPv6 guide. Browse the full networking tools hub for everything in one place.