IP Subnet Calculator
Enter an IPv4 address and CIDR prefix length to calculate the subnet's network address, broadcast address, and usable host range.
Last updated: September 5, 2026
Frequently asked questions
What is a CIDR prefix?
A number (0-32) after a slash indicating how many leading bits of the IP address are the network portion - /24 means the first 24 bits (three octets) identify the network, leaving the last 8 bits for host addresses.
How many usable hosts does a /24 subnet have?
254 - a /24 has 256 total addresses (2⁸), minus the network address and broadcast address, which aren't assignable to individual hosts.
What's the difference between network address and broadcast address?
The network address (all host bits set to 0) identifies the subnet itself and isn't assigned to any device. The broadcast address (all host bits set to 1) is used to send a message to every device on that subnet simultaneously - neither is usable as a regular host address.
Why do /31 and /32 subnets have no usable host range?
A /32 has exactly one address total (used to identify a single host, like a loopback interface), and a /31 has only 2 addresses with no room for separate network/broadcast addresses - both are typically used for point-to-point links where every address is directly usable.
How does the CIDR prefix length change if I switch from /24 to /25?
A /25 splits what would be one /24 network into two smaller subnets, each with 128 total addresses (126 usable hosts) instead of 256 (254 usable) - moving to a longer prefix always shrinks the address space per subnet while creating more subnets overall.
What's the usable host range for 192.168.1.0/24?
192.168.1.1 through 192.168.1.254 - the network address (192.168.1.0) and broadcast address (192.168.1.255) are excluded, leaving 254 assignable host addresses in between.
Is 'IP subnet calculator' the same tool as a 'CIDR calculator'?
Yes, essentially - both take an IP address and a prefix length (or combined CIDR notation) and compute the same network address, broadcast address, and usable host range; this tool takes the IP and prefix as separate fields rather than combined slash notation.