Subnet / CIDR Calculator
Enter an IPv4 address and prefix to get the network, broadcast, mask and host range.
Free • no sign-up • runs entirely in your browser.
What this calculates
Enter an IPv4 address with a CIDR prefix (for example 192.168.1.10/24) and this tool computes the network and broadcast addresses, the subnet mask and wildcard mask, the usable host range, and the total/usable host counts.
Quick CIDR reference
- /24 = 256 addresses (254 usable)
- /25 = 128 (126 usable)
- /30 = 4 (2 usable) — point-to-point links
- /32 = a single host
Frequently asked questions
What does the prefix (/24) mean?
It's the number of bits used for the network portion. /24 means the first 24 bits are the network and the last 8 identify hosts (256 addresses).
Why are there 2 fewer usable hosts?
The first address is the network identifier and the last is the broadcast address, so a /24 has 256 total but 254 usable host addresses.
What's the wildcard mask for?
It's the inverse of the subnet mask, used by ACLs and routing tools (e.g. Cisco) to match address ranges.