Subnet / CIDR Calculator
Quick Answer
A subnet calculator takes a CIDR block such as 192.168.1.0/24 and works out the network address, broadcast address, usable host range, and the number of usable hosts.
What Is Subnet / CIDR Calculator?
Subnet / CIDR Calculator is a free online network tools tool that calculate network address, broadcast, netmask and usable hosts from cidr. A subnet calculator works with CIDR notation to describe a range of IP addresses. CIDR (Classless Inter-Domain Routing) writes an address like 192.168.1.0/24, where the number after the slash is the prefix length — the count of fixed bits shared by every address in the block. From a CIDR block the tool derives the network address, the broadcast address, the first and last usable host addresses, and how many usable hosts exist (total addresses minus the network and broadcast addresses, except for the special /31 and /32 cases). Subnetting lets organisations divide a larger allocation into smaller, manageable networks for different departments, VLANs, or locations. A common stumbling block is the off-by-one between total addresses and usable hosts, and remembering that very small prefixes like /31 behave differently. This calculator handles IPv4 blocks and shows the full range at a glance. Unlike many similar tools, it runs entirely in your browser — no data is sent to any server, no account is required, and there are no usage limits. Whether you are a developer, writer, SEO professional, or casual user, this tool provides instant, accurate results without friction.
How to Use Subnet / CIDR Calculator
Enter an IPv4 address with its CIDR prefix (for example 10.0.0.0/24). The tool shows the network and broadcast addresses, the usable host range, and the host count. Calculation runs in your browser.
Key Features
- CIDR to network, broadcast, and usable range
- Usable host count for any prefix
- Subnet mask and wildcard mask display
- Handles edge cases like /31 and /32
Common Use Cases
- Planning IP allocation across VLANs or offices
- Checking whether two addresses are in the same subnet
- Documenting network ranges for a configuration
Common Mistakes to Avoid
- Confusing total addresses with usable hosts (minus 2)
- Forgetting that /31 and /32 are special cases
- Mixing IPv4 and IPv6 notation
Related Topics & Entities
- Subnet
- CIDR
- IP Addressing
Common Questions About Subnet / CIDR Calculator
Related Tools & Resources
- IP Lookup
- URL Encoder
Best Practices for Subnet / CIDR Calculator
To get the most out of Subnet / CIDR Calculator, follow these best practices. Ensure your input data is clean and properly formatted for the most accurate results. Use the copy function to transfer output directly to your clipboard. Bookmark the tool for easy access. Check the related tools section below for complementary utilities that can enhance your workflow. Remember that all processing is client-side, so your data never leaves your browser.
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Privacy & Security
Subnet / CIDR Calculator processes all data entirely within your browser using JavaScript. No text, files, or personal information is transmitted to any server. Your data stays on your device, making this tool safe for sensitive content. We do not track usage, store inputs, or share data with third parties. The tool works offline after the initial page load and requires no account to use.
Frequently Asked Questions
Find answers to common questions about this tool.