IP Subnet Calculator
Enter an IPv4 address and CIDR prefix to instantly get the network address, broadcast address, subnet mask, wildcard mask, and the full usable host range — all pure local math, with no network access involved.
All calculations happen locally inside your browser; this calculator never connects to any network.
What this tool does
Calculates a subnet's details from an IPv4 address and a CIDR prefix: network and broadcast addresses, subnet and wildcard masks, the first and last usable addresses, and how many there are.
When to use it
- Planning how to divide a network into subnets.
- Checking whether an address falls inside a given range.
- Configuring firewall rules or network routes.
- Learning how CIDR prefixes work in practice.
How to use it
- Enter the "IPv4 address".
- Enter the "CIDR prefix", for example 24.
- Read the results: network and broadcast addresses, both masks, the usable range and its size.
A practical example
Input
192.168.1.50 with a /24 prefix.
Output
Network 192.168.1.0, broadcast 192.168.1.255, mask 255.255.255.0, first usable 192.168.1.1 and last 192.168.1.254, with 254 usable addresses.
Limitations
- IPv4 only; IPv6 addresses are not supported.
- Invalid input is rejected with a clear message.
- Very narrow prefixes such as /31 and /32 have special cases in usable-address counting depending on how they are deployed.
Privacy and processing
All calculations happen locally inside your browser, and this calculator never connects to any network — it neither probes the address nor looks it up.
Technical notes
- The calculation is pure bitwise arithmetic on the address and mask, which is what makes it instant and exact with no external lookup.