IPv4 Subnet Calculator

What it does

An IPv4 address is 32 bits long, and subnetting uses a CIDR prefix (e.g. /24) to mark how many bits belong to the network. Given an "IP + prefix", this tool derives the network address, broadcast address, subnet mask, wildcard mask, usable host count, the first and last usable addresses, the binary form, the address class (A/B/C/D/E) and whether the range is private.

Besides IPv4 math, it labels the address class and flags private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 and similar). Everything is computed locally in your browser — nothing is uploaded.

Example

Enter 192.168.1.0/24 (or just the IP and pick prefix 24 from the dropdown):

Network address:  192.168.1.0
Broadcast address: 192.168.1.255
Subnet mask:      255.255.255.0
Usable hosts:     254
First usable:     192.168.1.1
Last usable:      192.168.1.254
Address class:    C
Private range:    Yes

A /31 prefix yields 2 usable hosts (point-to-point links) and a /32 is a single-host route with 1 usable host.