CIDR ↔ IP Range
Three tools in one: convert a CIDR block to its IP range; convert any IP range to the minimal list of CIDR blocks that cover it exactly; or paste a list of CIDRs and single IPs to aggregate them into the smallest possible set of summarised supernets. Everything runs client-side — no data leaves your browser.
Enter any CIDR notation — host bits are automatically masked to the network address.
The minimal set of CIDR blocks that cover exactly this range — no more, no less.
Enter CIDRs (e.g. 10.0.0.0/24) or single IPs — one per line. Adjacent or overlapping blocks are merged into the smallest covering supernet.
Use — Guide
How to use this tool
- Choose a tab: "CIDR → Range" to expand a CIDR block into its IP range, "Range → CIDR" to find the minimal CIDR blocks covering an address range, or "Aggregate" to summarise a list of CIDRs into the fewest supernets.
- In the "CIDR → Range" tab, type a CIDR block such as 10.0.0.0/24 — the first and last addresses, total address count, subnet mask and full range are shown instantly.
- In the "Range → CIDR" tab, enter a start IP and end IP (for example, 10.0.0.0 to 10.0.0.255) to get the minimal set of CIDR blocks that cover exactly that range.
- In the "Aggregate" tab, paste CIDRs or individual IPs one per line — adjacent and overlapping blocks are merged into the smallest covering supernets automatically.
- Use the copy icon on any individual result, or the "Copy all" button in the list tabs, to grab all values at once.
FAQ — Questions
Frequently asked questions
01What does CIDR notation mean?
CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length — for example, 192.168.1.0/24. The /24 means the first 24 bits identify the network; the remaining 8 bits identify hosts. CIDR replaced the older Class A/B/C system and allows much more flexible, efficient IP address allocation and route summarisation.
02How many usable hosts does a /24 subnet provide?
A /24 contains 256 total addresses (2^8). Two are reserved — the network address (the .0) and the broadcast address (the .255) — leaving 254 usable host addresses. For any prefix the formula is 2^(32 − prefix length) total addresses, minus 2 for usable hosts. Exceptions: a /31 (RFC 3021 point-to-point) has 2 usable addresses with no reserved network/broadcast, and a /32 is a single host route.
03Is my data kept private?
Yes. All three calculators — CIDR to Range, Range to CIDR and Aggregate — run entirely in your browser using JavaScript. No IP addresses, ranges or CIDRs are ever transmitted to Peritus Digital or any third party.
04Do I need a network engineer to design my IP addressing scheme?
For straightforward setups you can work through addressing manually with tools like this one. However, for multi-site networks, VLAN segmentation, firewall policy or any infrastructure with growth requirements, professional design saves time and avoids costly rework. Peritus Digital's Newcastle team provides managed IT and network design services for Hunter Region businesses — get in touch if you'd like expert advice.
More — Keep exploring
Related free tools
Want hands-on help, not just a check? Explore ourManaged IT & Support service.
Need help with your network?
From IP addressing to full network design — Peritus Digital can help.
Our Newcastle team designs and manages networks for Hunter Region businesses — VLANs, firewall rules, SD-WAN, structured cabling and everything in between. If you're working with CIDR blocks, you're probably planning infrastructure. Let's talk.