Free IP Subnet Calculator
Updated July 2026
Calculate subnet ranges, broadcast addresses, host counts, and wildcard masks from any CIDR notation. IPv4 and IPv6 subnetting — free online tool.
Diagnosing web and network issues quickly is critical for site owners, developers, and SEO professionals. The Subnet Calculator delivers actionable data in seconds.
Calculate subnet ranges, broadcast addresses, host counts, and wildcard masks from any CIDR notation. IPv4 and IPv6 subnetting — free online tool. Results are immediate — no waiting, no loading screens, no account required.
How to use the Subnet Calculator
Open the tool, enter your input, and get your result instantly. The interface is designed to be self-explanatory — no tutorial or manual needed. Where options exist, they are clearly labelled with sensible defaults. Your result can be copied to the clipboard or downloaded with a single click.
Tips for the best results
- Results reflect live server data — refresh to get the latest reading.
- Compare results across multiple URLs to identify inconsistencies quickly.
Who uses the Subnet Calculator?
- Network engineers planning IP address allocation for data center or office deployments.
- Students studying for CCNA and network certification exams practicing subnetting.
- System administrators configuring firewall rules and routing policies with correct subnet notation.
Common uses and search terms
The Subnet Calculator is frequently used for: subnet, CIDR, subnet calculator, network. Whether you need a quick result or are working through a longer project, the tool handles all common variations without any configuration.
Why use Allio Tools's Subnet Calculator?
Everything runs locally in your browser. No data is sent to a server, logged, or stored anywhere. The tool is completely free with no usage limits, no premium tiers, and no account required. Available in 11 languages and optimised for all screen sizes, the Subnet Calculator works on desktop, tablet, and mobile with no app download needed.
See also:IP Address Lookup · Website Speed Test · DNS Lookup
How the Subnet Calculator works
Enter an IP address with CIDR prefix length (e.g. 192.168.1.0/24) in the input field.
Click Calculate to instantly see: network address, broadcast address, first/last host, subnet mask, wildcard mask, and total host count.
View the subnet split table to divide the network into smaller subnets.
Enter any two IP addresses to check if they are in the same subnet.
Tips & tricks
- Run the Subnet Calculator before and after making server configuration changes to confirm the update took effect.
- Use the browser's Developer Tools alongside the Subnet Calculator for a complete picture of network and performance behaviour.
- Results reflect live data — re-run the check after a recent change to verify propagation across DNS caches.
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its subnet mask together: 192.168.1.0/24. The number after / is the prefix length — the count of bits used for the network portion. /24 = 255.255.255.0 mask.
How many usable hosts does a /24 subnet have?
A /24 has 2^8 = 256 addresses total. Subtract 2 (network address and broadcast address) = 254 usable host addresses. Formula: 2^(32-prefix) − 2 usable hosts.
What are common subnet sizes?
/30 = 2 hosts (point-to-point links), /29 = 6 hosts, /28 = 14 hosts, /27 = 30 hosts, /26 = 62 hosts, /25 = 126 hosts, /24 = 254 hosts, /23 = 510 hosts, /22 = 1022 hosts.
What is the difference between subnet mask and wildcard mask?
Subnet mask has 1s for network bits and 0s for host bits: /24 = 255.255.255.0. Wildcard mask is the inverse: 0.0.0.255. Wildcard masks are used in Cisco ACLs and OSPF configurations.
Can I calculate IPv6 subnets?
Yes. Enter an IPv6 address with prefix length (e.g. 2001:db8::/32) and the tool calculates the range, host count, and subnet breakdown. IPv6 /64 subnets are standard for LAN segments.
Is the Subnet Calculator free to use?
Yes, the Subnet Calculator on Allio Tools is completely free with no sign-up or registration required. It works directly in your browser.
How does the Subnet Calculator work?
Calculate subnet ranges, broadcast addresses, host counts, and wildcard masks from any CIDR notation. IPv4 and IPv6 subnetting — free online tool. No data is sent to a server — everything runs locally in your browser for maximum privacy and speed.
Do I need to install anything to use the Subnet Calculator?
No installation needed. The Subnet Calculator runs entirely in your web browser on any device — desktop, tablet, or mobile.
Is my data safe when using the Subnet Calculator?
Completely safe. The Subnet Calculator processes everything locally in your browser. No input data, results, or usage information is ever transmitted to or stored on any server.
Does the Subnet Calculator work offline?
After the page loads for the first time, the Subnet Calculator works without an internet connection for all client-side processing. Tools that fetch live external data (such as DNS or network lookups) require an active connection.
How current is the data returned by the Subnet Calculator?
The Subnet Calculator fetches live data in real time each time you run it. Results reflect the current state of the server or domain at the moment of the request.
Why does the Subnet Calculator sometimes return different results than other tools?
Results depend on the real-time state of the target server and DNS propagation, which can vary by geographic region and caching TTL. If you see inconsistencies, wait a few minutes and re-test — DNS changes can take up to 48 hours to propagate fully worldwide.
Does the Subnet Calculator work on all browsers?
Yes. The Subnet Calculator is built with standard browser APIs and works on all modern browsers including Chrome, Firefox, Safari, and Edge — on both desktop and mobile. No plugins, extensions, or third-party software are required.
How do I save or export my results from the Subnet Calculator?
Select and copy the result text to paste into any document or app. For image tools, a Download button saves the file directly to your device. Your browser's built-in screenshot function also captures results quickly. No account or login is required.
Works with ChatGPT, Claude, Cursor, GitHub Copilot, VS Code, Poe and more — 106+ tools, zero data collection.