Free IPv4 Subnet / CIDR Calculator

IPv4 Subnet and CIDR Calculator: Free, No Signup Needed, and Instant

Do you need to quickly figure out IPv4 subnets, network addresses, broadcast addresses, usable host ranges, or the number of hosts in a CIDR block? IPv4Hub.net has a free IPv4 Subnet / CIDR Calculator that was made just for network engineers, sysadmins, ISPs, hosting providers, data center operators, and anyone else who needs to manage IPv4 resources in today's scarce address market.

This tool gives you accurate results right away in your browser, whether you're planning a new subnet for cloud deployments, checking routing announcements, sizing blocks for BGP, checking allocations before buying or leasing IPv4 addresses, or just fixing network settings.

Why Use Our Free IPv4 Subnet Calculator?

No registration needed and it's free! You can use it as many times as you want without ads getting in the way or having to sign up.
Quick and light— Pure client-side JavaScript means no server delays and works offline after being loaded.
Correct IPv4 Calculations—Can handle any valid CIDR from /0 to /32 with the right math for networks, broadcasts, and hosts.
Results that are easy to read— Clearly shows:

Address for the network Address for the broadcast
Usable Host Range (the first and last usable IP)
Total Hosts That Can Be Used

Made for Real-World IPv4 Use — Great for ARIN/RIPE/APNIC/LACNIC/AFRINIC transfers, renting out clean blocks, avoiding reputation problems with big announcements, or making the most of your IPv4 inventory.
IPv4Hub.net is the trusted place to buy and sell verified, clean IPv4 blocks (/24 and larger). If you need IPs that actually route cleanly and have a good history, use the calculator and then look through our listings.

Type in your CIDR (for example, 192.168.1.0/24, 10.0.0.0/16, or 172.16.0.0/12) and click "Calculate." The results will show up in a few seconds.

Using the Free IPv4 Subnet / CIDR Calculator

Type or paste your IPv4 CIDR notation, which is an IP address followed by a prefix, like 203.0.113.0/24.
Press the button that says "Calculate."
See the instant breakdown:

Network: The subnet's base network address.
Broadcast: The address for the broadcast (not for hosts).
Usable Hosts: The first and last IP addresses that devices, VMs, and servers can use.
Count: The number of IPv4 addresses that can be used (2^(32-prefix) - 2 for most cases).

Want more? Look through our marketplace to find clean IPv4 blocks that are ready to rent or buy.

A lot of questions and answers: Everything you wanted to know about IPv4 subnetting and this calculator

Q: What is a subnet calculator, and why do I need one?
A subnet (or CIDR) calculator breaks an IPv4 network down into its most important parts: the network ID, the broadcast, the mask bits, and the usable IP addresses. In 2026, when IPv4 is still running out and transfers, leasing, and careful allocation are still necessary, quick subnet math will help you avoid mistakes in routing tables, firewall rules, NAT configs, or when buying blocks.

Q: Does this IPv4 subnet calculator work for all prefix lengths?
A: Yes, it works correctly with /0 through /32, even with edge cases like /31 (point-to-point, 0 usable hosts) and /32 (single host). Bitwise operations are used in the math to make it more precise.

Q: Does it work with IPv6?
A: Not yet. This tool is mostly about IPv4, where most of the problems with scarcity, pricing, and reputation still exist. We might add IPv6 later, but for now, take a look at our IPv4 market insights and tools.

Q: Is this good for classful subnetting (Class A/B/C)?
A: Yes, just type in the CIDR equivalent (for example, 10.0.0.0/8 for Class A private). It doesn't care about old class boundaries and uses CIDR logic from today.

Q: What should I do if I enter a CIDR that isn't valid?
A: The tool has basic validation and will let you know if your input is wrong (for example, if your IP octets are not valid or your prefix is outside of 0–32).

Q: How many hosts can a /24 actually use?
A: 254 usable hosts (256 total IPs minus network and broadcast).

Q: /23? /22?
A: /23 = 510 usable, and /22 = 1,022 usable. You can use the calculator for any size, which is great when you need to figure out how big of a block to rent or buy.

Q: Why does IPv4Hub give away this tool for free?
A: We're the best place for people who want to buy, sell, or rent IPv4. This calculator helps you plan exactly what you need to do, and then it helps you do it. You can look through our verified listings for /24, /23, /22, and larger blocks that have a clean history, no blacklists, and quick transfer support.

Q: Can the tool be used on a mobile device?
A: Yes, it works great on phones and tablets for checking networks on the go (data centers, colos, and remote troubleshooting).

Q: Is it possible to put this calculator on my own website?
A: The code only works on the client side, so feel free to change it (credit IPv4Hub.net). Or just link to ours!Q: How does this stack up against other free subnet calculators like SolarWinds, MxToolbox, jodies.de, and others?
A: Ours is made just for the IPv4 marketplace audience. It's simple, quick, and doesn't have any fluff or upsells to enterprise software. Many others require registration, show ads, or focus on diagnostics instead of just subnet math.

Q: What if I need a tool to change a range to CIDR or figure out the size of a block?
A: Good question! We are also working on those. Use this subnet tool to get started, and then come back or get in touch with us for help with IPv4 planning.

Q: Will using this tool hurt my IP reputation or leak data?
A: No, everything works in your browser. We don't send any IPs to our servers.

Q: I'm buying IPv4. How do I use this calculator?
A: Type in the block you're thinking about (or break up bigger allocations into smaller subnets that can be announced). Make sure the usable hosts meet your needs, that the prefix is BGP-friendly (at least /24 for many peers), and that there is no fragmentation that makes routing less efficient.

Q: Which size block calculator helps with leasing or buying IPv4?
A: All sizes! Figure out how many hosts you need for your use case (web hosting, VPN, cloud, IoT), and then compare that to our lease listings (usually /24–/20) or purchase options.

Q: Do you have any advice for subnetting in AWS, Azure, or GCP?
A: Yes, providers say that VPCs and subnets should start with /24 or larger. Use this tool to check for CIDR overlaps or figure out how to expand them.

Q: Will this tool become useless with IPv6?
A: Not for a while. IPv4 demand is still high in 2026 for old systems, some cloud providers, gaming, and areas where IPv6 adoption is slow. This calculator will be useful for a long time.

Ready to subnet in a smarter way? Try the Free IPv4 Subnet / CIDR Calculator now by scrolling up. Then, go to IPv4Hub.net to find clean, routable IPv4 blocks that will power your network.

Do you have any questions? Leave them in the comments or get in touch with our team. We're here to help you with all of your IPv4 needs.