Subnet Calculator
Calculates subnet details from CIDR notation (for example 192.168.1.0/24). Returns the network and broadcast addresses, first and last usable host, subnet mask, wildcard mask, host count, and IP class.
Frequently asked questions
- What does the number after the slash mean?
- The prefix length — how many bits belong to the network part. /24 means 24 network bits, leaving 8 host bits = 256 addresses. /16 gives 65,536. Smaller number = bigger subnet.
- What are "first usable" and "last usable"?
- The first and last address in a subnet are reserved (network address and broadcast). Everything between is assignable to hosts. In 192.168.1.0/24, usable is 192.168.1.1 through 192.168.1.254.
- When do I need a /31 or /32?
- /31 is for point-to-point links (just 2 addresses, no network or broadcast). /32 is a single host — often used for loopback interfaces or route targets.