How do I use this app?
Enter an IPv4 address, choose a CIDR prefix from 0 to 32, and review the calculated subnet details. Use Reset to start over.
IPv4 Subnet Calculator
Calculate network, broadcast, subnet mask, and host range from an IPv4 address and CIDR prefix.
Subnet input
Enter one IPv4 address and a CIDR prefix. Results update locally in your browser.
Use dotted decimal notation with four octets from 0 to 255.
Choose a prefix length from 0 to 32, such as 24 for a /24 network.
Subnet details
Enter an IPv4 address and CIDR prefix to see the subnet details.
Enter an IPv4 address and CIDR prefix to see the subnet details.
- Input
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- Prefix
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- Subnet mask
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- Wildcard mask
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- Network address
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- Broadcast address
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- First usable host
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- Last usable host
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- Total addresses
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- Usable hosts
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- Private range
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- Address class
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- Binary subnet mask
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When to use IPv4 Subnet Calculator
Common ways to use IPv4 Subnet Calculator:
- Plan a new subnet
Check the network, broadcast, and host range before assigning addresses.
- Validate CIDR notation
Confirm that an IP and prefix combination produces the expected boundaries.
- Troubleshoot routing
Compare calculated ranges with firewall, VPN, or router configuration.
- Share clean details
Copy formatted subnet facts into tickets, runbooks, or chat.
- Learn subnetting on mobile
Practice IPv4 subnet math on phone or tablet with a responsive layout.
FAQ
Is this app free to use?
Yes. The IPv4 Subnet Calculator is free to use and does not require an account.
What happens to my input data?
Your input stays in the browser. The calculator does not store subnet data or send it to a server.
Why am I getting an error or unexpected output?
Most errors come from malformed IPv4 addresses or CIDR prefixes outside 0 to 32. Check each octet and try again.
Where can I find instructions and troubleshooting tips?
Open the Help panel for subnet input rules, edge-case notes, and keyboard-friendly guidance.
How to use the IPv4 Subnet Calculator
Steps
- Type an IPv4 address such as 192.168.1.10. Each octet must be 0 to 255.
- Enter the CIDR prefix, for example 24 for a common private subnet.
- Review the calculated network, broadcast, mask, and usable host range.
- Use Copy results for tickets or Export JSON for documentation.
Tips
- All calculations run locally; your addresses are not stored or sent to a server.
- A /31 network shows both addresses as usable for point-to-point links.
- A /32 network represents one exact host address.
- Use Reset to clear the form before checking another subnet.