Free Subnet Calculator Online
IP subnet mask, network/broadcast address, usable hosts and CIDR notation
The Subnet Calculator breaks down any IPv4 address and CIDR prefix into its network address, broadcast address, subnet mask, and usable host range. Network engineers, system administrators, and students preparing for CCNA or CompTIA Network+ exams use it to plan IP address allocation without manual binary arithmetic. Enter an address like 192.168.1.0/24 and get every value you need in under a second.
Frequently Asked Questions
About the Subnet Calculator
Subnetting is the practice of dividing a single IP network into smaller, logically isolated segments. A /24 network gives 254 usable addresses, while a /26 gives 62 — choosing the right size prevents wasted addresses and limits broadcast traffic that degrades network performance.
Network engineers use subnets to implement security zones, separate VLANs, and control routing between departments. Getting the math wrong — even by one bit — can cause IP conflicts or unreachable hosts. This calculator eliminates that risk by computing every derived value from the CIDR notation you already know.
Whether you're planning a home lab, sitting for a certification exam, or designing a corporate LAN, the Subnet Calculator gives you the network address, broadcast address, subnet mask in both dotted-decimal and binary, wildcard mask, and the exact count of usable hosts — all without touching a calculator or opening a subnet cheat sheet.
When Should You Use This?
The Subnet Calculator is ideally suited for developers, network engineers, and IT professionals who need to perform quick, accurate calculations related to general calculations. Use this tool when you need to verify figures, compare different scenarios, or get a precise answer without manual computation errors.
What Does The Result Mean?
The calculated output provides an instant, accurate resolution to your input parameters. You can use these results directly for your planning, assignments, or professional tasks, knowing they are based on standardized formulas.
Example Calculation
Subnetting a /26 network for an office floor
📥 Inputs
- IP Address: 10.0.0.64
- Prefix Length: /26 (subnet mask 255.255.255.192)
🔢 Calculation Steps
- 1Block size = 256 − 192 = 64
- 2Network address = 10.0.0.64 (first address in block)
- 3Broadcast address = 10.0.0.127 (last address in block: 64 + 64 − 1)
- 4Usable host range = 10.0.0.65 → 10.0.0.126
- 5Total usable hosts = 2^(32−26) − 2 = 64 − 2 = 62 hosts
Limitations of this Calculator
- Results are based purely on the mathematical relationship of the inputs provided.
- Does not account for edge cases or extreme outlier values that fall outside standard formula constraints.
- Calculated outputs should be double-checked against your specific real-world requirements before finalizing important decisions.
How to Use the Subnet Calculator
- 1Enter your values into the Subnet Calculator input fields above.
- 2Review the input labels to ensure you are using the correct units.
- 3Click the "Calculate" button to get your instant result.
- 4Use the step-by-step breakdown to understand how the result was calculated.
- 5Export or copy your result to use in reports or share with others.
Tips & Best Practices
- CIDR /24 = 254 usable hosts, /16 = 65,534 hosts, /8 = 16,777,214 hosts.
- Double-check your input units before calculating — using the wrong unit is the most common source of errors.
- Bookmark this Subnet Calculator for quick access next time you need it.
- Use the share button to send your results to a colleague or save them for later reference.
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