About Subnet.im
Subnet.im is a free IPv4 subnet calculator and CIDR reference tool used by network engineers, system administrators, and IT students worldwide. Every calculation runs in your browser — fast, private, and instantly shareable via URL.
How It Works
Enter any IPv4 address and CIDR prefix length into the calculator. Results update instantly as you type — no submit button or loading required.
The calculator computes:
- Network address and broadcast address
- Subnet mask and wildcard mask
- First and last usable host addresses
- Total and usable host count
- Binary representations of all addresses
Results are encoded directly in the URL (e.g., subnet.im/10.0.0.0/24), so you can share or bookmark any calculation by simply copying the link.
All math runs in JavaScript in your browser. Nothing is sent to a server — your network information stays completely private.
Features
Instant Calculations
Results update as you type. No submit button, no loading spinners — just immediate feedback on any IP and prefix combination.
CIDR Cheat Sheet
Complete /0 to /32 reference table with subnet masks, wildcard masks, and host counts for every prefix length.
Shareable URLs
Every calculation has a unique URL. Share subnet details with your team by sending a link — no screenshots needed.
CIDR Reference Pages
Dedicated pages for each prefix length with detailed explanations, examples, and common use cases.
Dark Mode
Full dark mode support that respects your system preference. Toggle between light and dark themes at any time.
Mobile Friendly
Responsive design that works on phones, tablets, and desktops. Calculate subnets from anywhere, on any device.
Who Uses Subnet.im
Network engineers planning IP address allocation and subnetting schemes for enterprise networks. System administrators configuring firewalls, VLANs, and routing tables use it to quickly verify subnet boundaries and host ranges.
DevOps engineers setting up VPC subnets in AWS, GCP, or Azure rely on it for accurate CIDR calculations when provisioning cloud infrastructure. IT students studying for CCNA, CompTIA Network+, or other networking certifications use it as a learning and study aid.
Security professionals analyzing network ranges and access control lists, and anyone who needs a quick subnet calculation without installing software.
Built With
Built with Next.js and React. Styled with Tailwind CSS. Open source on GitHub.