CIDR Calculator
Convert between CIDR notation and subnet masks
What is a CIDR Calculator?
A CIDR Calculator converts between CIDR notation and subnet masks, helping network engineers quickly determine the subnet mask, wildcard mask, and host count for any CIDR prefix. CIDR (Classless Inter-Domain Routing) notation simplifies IP address management by representing network prefixes as a single number (e.g., /24).
This tool performs all calculations instantly in your browser with no server communication. Enter any CIDR prefix from /0 to /32 to get complete subnet information.
How to Use This Tool
- Enter CIDR prefix — Type a value between 0 and 32.
- Click Calculate — The tool computes subnet mask, wildcard mask, and host counts.
- Review results — Examine the binary representations and host calculations.
Common CIDR Prefixes
/8 (255.0.0.0) — Class A default, 16,777,214 usable hosts. Used for large enterprise networks.
/16 (255.255.0.0) — Class B default, 65,534 usable hosts. Common for medium-sized networks.
/24 (255.255.255.0) — Class C default, 254 usable hosts. The most common subnet for LANs.
/30 (255.255.255.252) — 2 usable hosts. Ideal for point-to-point router links.
/32 (255.255.255.255) — Single host. Used for loopback addresses and host routes.
How to Use This Tool
- Enter your input — Provide the value required by CIDR Calculator (e.g., IP, domain, text) in the input field above.
- Configure options — Adjust any settings such as CIDR, key length, or format if the tool provides them.
- Click Calculate/Generate — Results appear instantly in the results panel below.
- Copy or export — Use Copy All or Download (CSV/PDF) to save results. All processing stays in your browser.
Understanding the Results
Output format: Convert between CIDR notation and subnet masks. Results are shown with clear labels and can be copied for documentation, ticketing, or IPAM systems.
Accuracy: Calculations follow current RFCs and browser-native crypto where applicable. For DNS/WHOIS lookups, results reflect live network responses at query time.
Tips & Best Practices
• Keep inputs in correct format (e.g., valid IPv4 like 192.168.1.1, valid domain like example.com) to avoid validation errors.
• Bookmark this tool and try related tools: IP Tools utilities are linked below as Related Tools.
• All NETCUE tools run client-side — no data leaves your browser. For sensitive data, you can use them offline after first load.
Frequently Asked Questions
/24 means the first 24 bits of the IP address are used for the network portion, leaving 8 bits for hosts. This gives 256 total addresses (254 usable).
CIDR allows variable-length subnet masks, eliminating the rigid Class A/B/C boundaries. This enables more efficient IP address allocation and reduces waste.
/32 represents a single host address (255.255.255.255). It is commonly used for loopback interfaces and specific host routes.
Yes — every NETCUE tool, including CIDR Calculator, is free, requires no login, and runs entirely in your browser. No input is sent to any server.
No. CIDR Calculator processes everything locally via JavaScript. Closing the tab clears the in-memory input. We do not log, store or transmit your data.
Convert between CIDR notation and subnet masks — built for network engineers and developers, with instant results, copy/export, and related ip tools tools one click away.
Yes. After the page loads once, it works offline (service worker cache) and is fully responsive on mobile. Inputs stay 16px to avoid iOS zoom.
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