Identify the class and scope of an IPv4 address
Enter any IPv4 address to find its classful range (A, B, C, D or E), the default mask for that class, its typical use, and its scope — public, private, loopback or link-local. This is handy for students learning networking and engineers quickly checking whether an address is routable.
How it works
The class is read from the first octet of the dotted-decimal address. The calculator then applies the matching default mask and checks the address against the standard reserved ranges (RFC 1918 private, 127.0.0.0/8 loopback and 169.254.0.0/16 link-local) to determine scope.
| Class | First octet | Default mask | Typical use |
|---|---|---|---|
| A | 0–127 | /8 (255.0.0.0) | Very large networks |
| B | 128–191 | /16 (255.255.0.0) | Medium networks |
| C | 192–223 | /24 (255.255.255.0) | Small networks |
| D | 224–239 | — | Multicast |
| E | 240–255 | — | Reserved/experimental |
Example
For 192.168.0.1, the first octet is 192, so it is Class C with a default /24 mask. It falls inside 192.168.0.0/16, so its scope is flagged as RFC 1918 private — not routable on the public internet.
All analysis runs in your browser; no address is uploaded.