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Try IPv4 Subnet Calculator

Why subnet math matters

Network engineers, developers, and homelab builders constantly translate between IP addresses, CIDR notation (like /24), and usable host ranges. Getting the network and broadcast wrong breaks routing, DHCP scopes, and firewall rules. A quick calculator removes arithmetic mistakes and speeds up documentation.

What this tool shows

Given any IPv4 address and prefix length, you get:

  • Network address and broadcast
  • Subnet mask and wildcard mask (useful for ACLs)
  • First and last usable host for typical LAN subnets
  • Total addresses and usable hosts (with notes for /31 and /32)

Typical uses

  • Planning VLANs and static assignments
  • Verifying cloud security group CIDRs
  • Studying for CompTIA, CCNA, or similar certifications

Disclaimer

Addressing rules can vary by vendor (especially for /31 point-to-point links). Always confirm against your platform’s documentation.