About this tool
An IPv4 subnet calculator turns an address and prefix length into the values engineers actually use: network address, broadcast address, subnet mask, usable host range and host capacity. It is useful when checking a handoff, reviewing an IP plan, or confirming whether an address belongs inside a proposed subnet.
The calculator treats the CIDR prefix as the boundary between network and host bits. For example, a /24 leaves eight host bits, while a /30 leaves only two. The usable-host count follows traditional IPv4 subnet rules and excludes the network and broadcast addresses where applicable.
How to use it
- Enter an IPv4 address followed by a CIDR prefix, such as 192.168.10.34/24.
- Select Calculate.
- Use the returned network, broadcast, mask and host range to validate your design or ticket notes.
Example: 192.168.10.34/24
A /24 has a mask of 255.255.255.0. The network is 192.168.10.0, the broadcast is 192.168.10.255, and the traditional usable range is 192.168.10.1 through 192.168.10.254 for 254 usable hosts.
Engineering notes
- For point-to-point links, operational practice may use /31 rather than the traditional /30. Verify what the devices and your design standards support.
- Do not assume two addresses are in the same subnet just because the first three octets match; the prefix length determines the boundary.
Frequently asked questions
What does /24 mean?
It means the first 24 bits identify the network and the remaining 8 bits identify addresses inside that subnet.
Why are network and broadcast addresses normally not assigned to hosts?
They have special meanings in traditional IPv4 subnetting. The network identifies the subnet itself and the broadcast addresses all hosts in that subnet.
Can I enter any host address inside the subnet?
Yes. The calculator derives the subnet boundary from the address and prefix.