Processed locally in your browser — not uploaded
CIDR Calculator
Enter an IPv4 address in CIDR notation to get the network address, broadcast address, usable host range, subnet mask, wildcard mask and total address count. Handles /31 point-to-point and /32 host routes correctly. Runs entirely in your browser.
- Network Address
- 192.168.1.0 First IP of subnet
- Broadcast Address
- 192.168.1.255 Last IP reserved for broadcast
- First Usable Host
- 192.168.1.1 First assignable IP
- Last Usable Host
- 192.168.1.254 Last assignable IP
- Subnet Mask
- 255.255.255.0 Dotted decimal subnet mask
- Wildcard Mask
- 0.0.0.255 Inverse of subnet mask
How to use
- Enter an IPv4 address with a CIDR prefix, e.g. 192.168.1.0/24.
- The network address, broadcast address, usable host range and subnet mask update as you type.
- For /31 and /32 blocks, the usable range follows RFC 3021 (point-to-point) and single-host conventions rather than the standard network/broadcast split.
Understanding the output
Usable hosts excludes the network and broadcast addresses for prefixes /30 and shorter. /31 blocks (2 addresses) are treated as point-to-point links where both addresses are usable, per RFC 3021. /32 is a single host route.
Common issues & tips
- •Invalid IPv4 address: each octet must be 0-255, and the address needs exactly four octets.
- •Invalid prefix: must be a whole number between 0 and 32.
Frequently asked questions
- Why does /31 show 2 usable hosts instead of 0?
- Per RFC 3021, /31 subnets are a special case for point-to-point links: both addresses are usable and there's no separate network or broadcast address.
- Does this support IPv6?
- Not currently — this calculator handles IPv4 CIDR notation only.
- Is my input sent to a server?
- No. All calculation happens locally in your browser.
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