Subnet calculator
Subnet Calculator
Enter an IP address and prefix length to get the network, host range, and mask details instantly.
Start with any IPv4 address. Results update live as you type.
Quick guide
- Use the prefix length to control how many hosts live inside the subnet.
- Network and broadcast boundaries update automatically from the IP and prefix.
- /31 and /32 are special cases for point-to-point and single-host links.
CIDR preview
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Subnet summary
Network address
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Network CIDR
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Broadcast address
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Input IP role
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Host range
Usable range
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Usable hosts
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Host bits
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Total addresses
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Block size
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Mask details
Prefix length
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Subnet mask
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Wildcard mask
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Binary view
IP address
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Subnet mask
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Network address
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Common masks
Notes for planners
/31 subnets are commonly used for point-to-point links and treat both addresses as usable.
/32 represents a single host route, so network and host address are the same.
For larger allocations, use the total address count to estimate capacity before adding reserved ranges.
How it works
Parses your IPv4 address and prefix, builds the subnet mask, and derives network, broadcast, usable range, and binary views entirely in the browser.
- Usable hosts drop as the prefix grows (/32 is a single host, /31 is point-to-point).
- IPv6 is not supported here; this tool focuses on IPv4 CIDR.
Quick examples
Copy any value to clipboard with the buttons above each card.
Mini FAQ
Why are two addresses unusable on /24?
Network and broadcast addresses are reserved on prefixes up to /30.
When do /31s make sense?
Use /31 for point-to-point links where both addresses are endpoints.
Why is my CIDR not applied?
Ensure the format is IP/prefix (e.g. 203.0.113.5/27) and the prefix is 0–32.
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